Fog-IndexFog-Index

Updates

What's new with Fog-Index — algorithm improvements, new features, and under-the-hood changes to help you chase fog with more confidence.

Feature

October 2026 updates

A collection of algorithm and product improvements shipped in October 2026.

Nearby Fog, and Fog Level

When your spot looks clear but the low ground around it is filling with fog, Fog-Index now tells you which way to drive, toward which town, and when the fog starts.

  • Every forecast also checks up to eight areas about 7 miles out around each saved spot. A new Nearby row on the card reads like "Fog S to W · toward Vancouver · lower ground · from 6 AM", with a small compass showing the foggy directions. It stays on the card even on mornings below your threshold, which is exactly when it matters.
  • Open the details for the full picture: each foggy direction with its town, which of your other saved spots lie that way and how they score, and a link that opens the fog map on that same morning (Chaser covers 2 mornings, Pro 4).
  • Nearby fog comes from a single model, so it is a clue rather than a promise: it never changes your Fog Score and never sends an alert by itself. It rides along in the alerts, digests and reminders you already get, and the digest now shows it on below-threshold mornings too.
  • "Fog position" is now "Fog level", with one set of words for every spot: below you, at your level, or above you, plus near your level when the fog top is too close to call. "Fog around you" is gone, so it can't be confused with fog nearby. On an overlook with the fog below you, thickness now describes the valley fog you'll be looking down on.
  • Cards, the details panel and emails now share one order: thickness, fog level, nearby fog, then the light. Every link in an email opens that exact morning with the spot highlighted, instead of today's forecast.
  • Scout members see a heads-up when fog is forecast nearby; Chaser and Pro show where.

Fog Density Is Now Fog Thickness

The surface-fog read has been renamed and redrawn around the question photographers actually ask: will light break through? It is now Fog Thickness, with four levels on one scale, shown the same way everywhere.

  • Four ordered levels replace the old names: Thin, Layered, Thick, and White-out. Thin and Layered let light break through; Thick and White-out do not. Layered is still the sweet spot. Pair it with Sky Above to know whether there is light up there to break through.
  • One scale, one look. Thickness is drawn as a fog ramp, where lighter means thicker, on the map, on your location cards, in the table, in the detail panel, and in your alert emails. The colours you already know from the Fog Score (green, blue, amber) now mean score only, never thickness.
  • Heavy rain at sunrise is no longer shown as a kind of fog. Those cells are hatched and labelled "Rain at sunrise, no fog read", and the grid-cell count banner is gone.
  • The map's two layers are now Score and Thickness, and both obey your threshold, so the map and your cards can never disagree about the same spot. The Threshold control is available on both.
  • The map's score colours now match the score ring on your cards exactly: 85+ is green, 70 to 84 is blue, 60 to 69 is amber. A 75 is the same colour everywhere.
  • The About page and the "Above the Fog or In the Soup" article have been updated to the new names.

Location Cards Now Lead With the Decision

Each card answers two questions at a glance, go or not and what kind of morning, and leaves the explanation to the detail panel.

  • Three labelled rows sit right under the score: Thickness (can light get through the fog), Position (are you above it or in it), and Light (is there light above to break through). Below your threshold they collapse to one line, and Light stays visible.
  • A small confidence read beside the score, one dot per source, shows how many checks confirm the forecast. Hover or tap it for the full list.
  • Coordinates, the weather-input grid, and the signal row have moved to the detail panel, where the detail panel now opens with the fog cues first and the inputs after.
  • Cards are about a third shorter, so you can compare more spots without scrolling.
Feature

September 2026 updates

A collection of algorithm and product improvements shipped in September 2026.

Overlook Mode: Is the Fog Below You?

Save a viewpoint like Angel's Rest and Fog-Index now forecasts the valley floor beneath it too, then tells you in one line whether the fog will be below you, around you, or above you.

  • When terrain detection finds a real overlook, at least 100 ft above the lowest nearby ground, overlook mode switches on by itself, including for overlooks you saved before this release. You can turn it on or off when adding a location or in Edit Alert.
  • Switching it on in Edit Alert checks the ground around your spot right there in the dialog and refreshes the forecast at once, so the fog position is on the card when you close it. A spot that does not qualify says so before anything is saved, with the numbers.
  • The card leads with the better of the two forecasts: your spot's own score and the fog in the valley below. A small caption keeps both numbers in view.
  • Fog position replaces the Fog height and At this spot readings on overlook locations, with a cross-section drawn from a real elevation transect through your pin. The fog band is drawn only as confidently as the estimate behind it: crisp when confidence is high, blurred across its margin when medium, not at all when low.
  • Alerts for overlooks fire when either your spot or the valley floor clears your threshold, and the subject line says where the fog sits: "Fog below you".
  • Flat locations are unchanged: there is no valley to score and nothing to draw, so those cards keep today's readings.

Ridges Are No Longer Penalized

Ridge and overlook locations are no longer marked down just for being high ground. Standing above a fog-filled valley is one of the best mornings in fog photography, and the score should not be tilted against the places you go to see it.

  • The old ridge penalty double-counted what the forecast already knows: the air at a ridge is usually drier and windier than the valley floor, and that is already in the hourly inputs. Removing the extra deduction gives ridge locations a small, uniform lift on every morning; nothing else in the score moves.
  • Upslope fog is unchanged: when moist wind is pushed up a slope, ridge locations still get their upslope bonus in the transport pathway.
  • Fog Seasonality recomputes ridge locations on the same rule, so month-by-month ridge tendencies rise slightly to match. Valley, river, lowland, coastal and urban climatology is unchanged.
  • Overlook mornings deserve better than a single score at the spot you stand on, which is why this release ships alongside Overlook Mode above: the valley floor gets its own forecast and the card says whether the fog is below you.

Terrain Detection Finds Overlooks, and Explains Itself

Adding a location now recognizes Gorge-style overlooks, stops mistaking big rivers for the ocean, and shows why a terrain was suggested instead of applying it silently.

  • Promontories and cliff-edge viewpoints in steep terrain, like Angel's Rest, Crown Point, Rowena Crest and Rattlesnake Ledge, are now recognized as Ridge / highland instead of falling back to General. In our test of 78 real places, correct suggestions went from 42 to 66.
  • Riverside spots along the Columbia (Hood River, Cascade Locks, the base of Multnomah Falls) were being tagged Coastal because the river counted as sea. Coastal now requires real ocean nearby, which also makes coastal detection work outside the US.
  • A cliff top far above a river is no longer called a floodplain, small towns are no longer called Urban just because they have a name, and flat high basins are no longer called ridges because of their altitude.
  • Only a strong match is applied automatically, and even then the card stays on screen with the reasons and a one-tap way back to General. Possible matches ask first. When nothing fits, you see the closest lean and what the terrain shape shows, instead of a dead end.
  • Re-detect in Edit Alert now runs the same analysis as adding a location, and Fog Seasonality re-checks previously detected terrain once so existing locations pick up the fix.
  • Tapping the map to move the pin no longer zooms the map back out. The map stays where you zoomed it; only a search pick reframes it.

See What's Actually Happening Outside

Your saved locations now show what the nearest weather station is reporting right now, next to what the National Weather Service forecasts for your sunrise window. And when a forecast changes its mind overnight, the card says so in plain words instead of quietly showing a different number.

  • A new nearby-observation panel reports the current condition at the closest suitable weather station, when it was observed, which station it is, how far away, and how much higher or lower than your spot. Fog, mist, low cloud, and reduced visibility are named separately, because they are very different mornings to drive toward.
  • Observations work worldwide through NOAA's global aviation weather network, wherever a suitable station reports nearby. Matching normally uses a 15 km radius with a limited relaxation to 20 km, and it respects your miles-and-feet or kilometres-and-metres setting.
  • The panel stays on the card even when the forecast has not changed, is still loading, or is unavailable. Current conditions are their own thing, not a footnote on a score.
  • US locations also show the ordinary National Weather Service forecast for your exact sunrise window, so you can see when we and the NWS disagree. This is the routine area forecast; the existing confirmation badge, now labelled NWS advisory, still means an official Dense Fog or Freezing Fog hazard notice.
  • When a morning's Fog Score falls sharply from its recent high, the card now explains it: what it was, what it is now, and that fog is still possible. Previously the number simply changed with no explanation.
  • The Fog Score lost its percent sign. It is a 0-to-100 score for how favorable conditions are, not an 80% chance of fog, and showing it as a percentage claimed a precision we do not have. Real percentages like humidity and cloud cover keep theirs.
  • Mornings that have already finished are now clearly labelled as final forecasts rather than looking like live conditions.
  • Behind the scenes we are testing two fixes to how the score handles very light wind and the minutes just after sunrise. They run quietly alongside the current scoring and are being graded against real station observations. Nothing about your scores or alerts changes unless and until that testing earns it.
Improvement

Planning Emails Now Follow Your Home Timezone

Fog-Index planning emails now arrive on your schedule, wherever home is. Daily summaries, night-before reminders, weekly outlooks, and Quiet Hours all use one editable Home timezone instead of a fixed Pacific schedule.

  • Daily summaries arrive around 5:00 PM, night-before reminders around 8:15 PM, and weekly outlooks Thursday at 8:00 AM in your Home timezone.
  • A new Home timezone setting under Notifications & Alerts lets you search by city, choose your device timezone, or correct the setting at any time.
  • Your Home timezone stays fixed when you travel, so a trip does not unexpectedly move your delivery schedule. It changes only when you choose a new one.
  • Planning emails and real-time alert Quiet Hours now follow the same Home timezone, with planning emails waiting until Quiet Hours end when needed.
  • Forecast dates and sunrise windows always show the location's local date, time, and timezone, while each email footer confirms the timezone used for delivery.
Launch

July 2026 updates

A collection of algorithm and product improvements shipped in July 2026.

The Fog Map Goes Worldwide

The Fog Potential Map now covers the entire planet. Every coastline, valley, and mountain range where a sunrise happens gets a daily fog score — from the Dolomites to New Zealand, and for the first time, Alaska and Hawaii.

  • Worldwide coverage at the same base detail as the US map, refreshed every morning from a global weather model.
  • Offshore fog banks count too: scoring extends roughly 50 miles into coastal waters, where the marine layer forms before it rolls in.
  • The US keeps its extra-detailed layers (Pacific Northwest, Columbia River Gorge, Mount Rainier, Yosemite Valley) — worldwide coverage is the floor, not the ceiling.
  • You can now zoom out further to browse whole continents at once.
  • Fog density and signal confirmation remain part of the detailed US coverage for now — international extra-detail regions come next, guided by where members actually chase fog.

Fog Spotlights: Free Live Forecasts For Iconic Locations

Fog Spotlights are free, public forecast pages for legendary fog locations — a live Fog Score, nearby webcams to verify it with your own eyes, and month-by-month seasonality for trip planning. No account required.

  • The Spotlight hub at /spotlights launches with four locations: Yosemite Valley, Mount Rainier Paradise, the Columbia River Gorge, and the Del Norte Redwoods.
  • Each Spotlight pairs the live Fog Score with webcams pointed at the scene, so you can watch a forecast verify in real time.
  • A month-by-month Fog Seasonality section shows each location's peak fog stretch — useful long before the forecast window opens.
  • Every Spotlight is a permanent, shareable link. Send one to a shooting partner before the next promising morning.
  • When a Spotlight earns your trust, you can save that exact viewpoint as your own tracked location and get fog alerts for it.

Sharper Fog Seasonality In Valleys And Mountains

Fog Seasonality — the 10-year historical layer behind month-by-month planning — now reads terrain much more faithfully. Valley and mountain locations get noticeably more accurate fog tendencies; coastal spots stay essentially unchanged.

  • The historical archive now uses a finer-grained reanalysis that tracks temperature and moisture at much higher ground detail — the difference matters most in valleys, foothills, and complex terrain.
  • Inland and mountain locations may show stronger fog seasons than before. Yosemite Valley's spring fog season, for example, now surfaces the way photographers actually experience it.
  • Under the hood we also fixed a data-request bug that had quietly served a generic model blend instead of the intended research-grade climate record.
  • Curious how it all works? We published a companion deep-dive on the blog: The Mechanics of Fog Seasonality.
Feature

Past Mornings For Saved Forecasts

Chaser and Pro members can now review recent completed mornings from the same saved-location forecast tabs. It is built for comparing the final forecast with the fog you actually saw, photographed, or missed.

  • A new past-mornings tab swaps the existing forecast strip backward without moving the cards or table below.
  • Past review uses the last saved forecast before the sunrise window ended, so the score reflects what Fog-Index knew before the morning was over.
  • Sort and card/table views work the same way in past mode, with favorable-count badges replacing actionable alert counts.
  • Chaser includes 3 days of past review, while Pro includes 7 days.
Feature

April 2026 updates

A collection of algorithm and product improvements shipped in April 2026.

Fog Seasonality Arrives For Saved Locations

Saved locations can now switch from Forecast to Seasonality to see when a place usually gets foggy across the year. It is built for long-range planning: comparing locations, spotting peak months, and timing trips before the short-range forecast window even begins.

  • Saved locations now include a new `Forecast | Seasonality` mode with month-by-month fog tendency built from a rolling 10-year historical archive.
  • Seasonality uses stacked Likely + Possible views so you can compare places quickly, then drill into a single location to inspect monthly and weekly timing.
  • The historical layer is point-based and shared across matching saved spots, which keeps common viewpoints fast and reusable as the feature grows.
  • Fog Seasonality is a planning tool, not a guarantee. Use it to choose when to go, then rely on the live forecast to decide whether the upcoming window is worth the alarm.

Spring Wet-Ground Memory + Better Sheltered Valley Calls

Fog-Index now does a better job remembering when the ground is still wet, even after the rain stops. That helps spring valleys, soaked meadows, and post-storm mornings show up more realistically in your forecasts.

  • Saved-location forecasts now keep more wet-ground memory when recent rain or saturated soil suggests the landscape is still feeding morning fog.
  • This especially helps spring mornings in valleys and lowlands where snowmelt, flooded meadows, or lingering soil moisture can support fog without fresh overnight rain.
  • We also softened a common false negative on saved locations in sheltered valleys, so some gusty clearing-storm setups are less likely to be dismissed too aggressively.
  • Forecast setup, manual refresh, previews, the free location check, and the Fog Potential Map now share the same upgraded wet-ground logic for more consistent reads.
Improvement

March 2026 updates

A collection of algorithm and product improvements shipped in March 2026.

Alerts UX Refresh: Faster Scanning, Smarter Defaults

The Alerts dashboard now surfaces the most important information sooner, with clearer hierarchy and defaults tuned for quick morning decisions.

  • A new dynamic alerts header now highlights horizon summary and best upcoming window at the top of the page.
  • Sorting now defaults to Top score, so your strongest opportunities rise to the top automatically.
  • Alert counts are now surfaced more clearly to improve at-a-glance awareness across your forecast horizon.

Fog Density + Clearer Planning Context

Fog-Index now separates surface-level fog density from above-fog planning, making saved-location forecasts easier to read whether you want to shoot in the soup or climb above it.

  • New Fog Density labels describe what the air should feel like at your saved spot, from subtle mist to white-room risk.
  • Fog Height remains the elevation-planning cue, helping you judge whether your spot is likely above the layer or inside it.
  • Planning context now more clearly separates surface atmosphere, above-fog decisions, and light above the fog.
  • The map now supports a Fog Density view for surface-opacity scouting, while Fog Potential remains the default layer.

Transport Pathway Upgrade: Upslope Mode + Fallback Clarity

Fog-Index now treats Pathway 2 as a broader transport engine for marine, inland advection, and ridge upslope setups. We also replaced ambiguous fallback blanks with clear diagnostics so inland advection windows are easier to trust.

  • A conservative upslope branch now activates for ridge locations when fallback transport is moist and wind-supported, instead of always penalizing ridge terrain.
  • When upslope mode is active, ridge and inland fallback penalties are bypassed so valid mountain-lift events are less likely to be suppressed.
  • Advection fallback rows on cards and table now show diagnostics (Cooling Source, Climatology, Inland Penalty) instead of all `--` placeholders.
  • Fog-type labels now clearly separate `Marine Fog`, `Advection Fog`, and `Upslope Fog` based on the active reason codes.

Calmer-Night Memory + Clearer Fog-Type Signals

Fog-Index now remembers overnight wind conditions for radiation-fog setups instead of judging only the final pre-sunrise hour. We also improved how score-driver metrics are shown so each forecast window better explains whether radiation or marine transport is driving the call.

  • Radiation scoring now checks the overnight prep window, so a brief calm snap right before sunrise is less likely to overstate fog potential after a windy night.
  • Gentle, steady overnight winds are now treated as a positive setup signal for stable boundary-layer development in radiation-fog scenarios.
  • Saved-location cards and table views now show pathway-aware score drivers, helping you quickly interpret inland cooling setups versus coastal transport setups.
  • When marine context is unavailable, pathway-specific fields stay neutral and surfaces gracefully show placeholders instead of forcing a misleading value.

Saved-Location Planning Context: Cloud Layers + Fog Layer Estimates

Saved-location forecasts now include planning context for photographers once a morning looks promising: cloud-layer breakdowns for light quality and conservative fog-layer estimates to help with vantage-point decisions.

  • Your saved locations now show low, mid, and high cloud layers plus a Sky Above read, so you can judge whether the light above the fog looks open, filtered, or blocked.
  • We added a fog layer estimate with an above-fog verdict for saved locations, using the location's elevation to help answer whether your spot is likely above the deck, in it, or still uncertain.
  • These planning cues appear on saved-location forecasts and related alert surfaces. They are not a new global fog-height map layer.
  • Coverage follows the saved-location forecast pipeline, so it can work outside the US anywhere Open-Meteo supports the forecast. US-only limits still apply to NWS advisory confirmation, and the separate Fog Potential Map remains CONUS.
Algorithm

February 2026 updates

A collection of algorithm and product improvements shipped in February 2026.

Global Coastal Upgrade + Better Rainy-Front Fog Detection

Fog-Index now scores marine fog using ocean temperature physics instead of fixed regional presets, which improves consistency across coastlines worldwide. We also added a dedicated rainy-front fog check to better catch saturation events during light-rain setups.

  • Coastal advection scoring now uses air-vs-sea temperature contrast with onshore wind geometry, so behavior is more portable across different countries and coast orientations.
  • A new frontal fog gate can raise fog potential when recent rain and rapid moisture increase point to precipitation-driven fog formation.
  • The same upgraded model path now powers location setup, manual refresh, scheduled alerts, daily digest, and the Fog Potential Map for strict parity.
  • If marine context is temporarily unavailable, the model falls back gracefully instead of switching to a separate algorithm family.

Terrain Hint Recommendations + Easier Override

Adding a location now includes terrain analysis from coordinates, with safer rules that recommend a terrain only when signals are strong enough. General remains the default when terrain is mixed or unclear.

  • New location setup now analyzes terrain in the background and may recommend hints like coastal, river, valley, ridge/highland, or urban.
  • Terrain recommendations stay conservative by design: if confidence is low or mixed, Fog-Index keeps General instead of forcing a terrain override.
  • Fog Seasonality now resolves better historical terrain context for weak saved hints, which improves coastal and river climatology at many locations.
  • Urban handling is now stronger in city cores to reduce false river or valley calls from mixed metro terrain.
  • Existing saved locations can be re-checked from Edit Alert with the Re-detect action, and manual selections still win.

Valley Inversion Support: Better Deep Winter Fog Calls

Fog-Index can now detect the classic winter inversion setup where warmer air sits above a cold valley floor. This helps the model hold onto persistent valley fog later into the morning instead of burning it off too aggressively.

  • The model now checks vertical temperature layers, not just surface cooling. If air above is warmer than the surface, that's a strong trapped-fog signal.
  • When conditions match a true winter stagnation setup (valley-like terrain, very light wind, strong inversion), fog persistence is scored more conservatively after sunrise.
  • Pressure-fall penalties are softened during stagnation events, because those pressure changes don't always clear deep valley inversions right away.
  • Best results come when your terrain hint is accurate — especially valley, river, or lowland locations where cold air pooling is common.

Marine Fog Support: The Coastal Blanket

Fog-Index now understands marine fog — the thick, wind-driven coastal layers that define Pacific Northwest summers and San Francisco year-round. The algorithm runs two scoring pathways in parallel and automatically picks the one that best fits conditions at your location.

  • A brand-new advection fog scoring pathway runs alongside the existing radiation fog model. The algorithm evaluates both and keeps the higher score, so you always get the most accurate prediction for your spot.
  • The old model penalized wind — which is exactly wrong for coastal fog, where moderate onshore breezes push marine air inland. The new pathway flips this: 5-12 mph winds from the ocean are now a strong positive signal.
  • Wind direction matters. The model now checks whether wind is blowing from the ocean toward land (onshore flow), a key ingredient for marine fog formation along coastlines.
  • Your location cards and email alerts now tell you which type of fog to expect — "Marine Fog" or "Valley Fog" — so you know what kind of conditions to prepare for.
  • The fog potential map also scores marine fog. Coastal grid cells can now light up during summer marine layer events that the old map would have missed entirely.
  • Summer is no longer a dead zone. Marine fog peaks June through September, exactly when radiation fog is at its weakest. This fills a major seasonal gap in the model.

Smarter Fog Predictions: Dew Detection & Seasonal Dissipation

Two physics-based improvements make the fog score more accurate on very calm nights and throughout the morning hours across all seasons.

  • The algorithm now distinguishes between dew and fog. Very calm, wet nights are more likely to produce dew on the grass than fog in the valley — scores are adjusted accordingly.
  • Fog "burn-off" predictions are now season-aware. Winter morning fog lingers longer because the sun is low and weak, while summer fog dissipates faster under strong solar heating.
  • In previous versions, a single daytime penalty was applied year-round. The new system uses a graduated multiplier that varies by both season and hours after sunrise.
  • These changes were informed by an independent review of the algorithm against established radiation fog physics.
Feature

Interactive Fog Potential Map

A brand-new map view lets you scout fog potential across the entire continental United States at a glance — no saved locations required.

  • An interactive heatmap overlay on top of Google Maps shows fog likelihood for every sunrise window across the continental US.
  • Color-coded grid cells make it easy to spot promising valleys, river corridors, and coastlines: green for likely fog, amber for possible, and faint for unlikely.
  • Toggle between three forecast days to plan your shoots ahead of time — see fog potential for today, tomorrow, and the day after.
  • The map uses the same scoring algorithm as your saved locations, with a daily precomputed grid across the continental US plus focused high-resolution regional overlays.
  • Available for Pro subscribers.
Launch

Fog-Index Launches

After months of development and dozens of algorithm iterations, Fog-Index is live — purpose-built for landscape photographers who chase fog.

  • A proprietary 0-100 fog likelihood score that goes far beyond simple humidity checks, accounting for dewpoint depression, wind regimes, cloud timing, terrain, pressure trends, and more.
  • 7-day hourly forecasts with sunrise-window focus — the score highlights the exact hours fog is most likely to form and persist.
  • Multi-source weather data combining Open-Meteo, Tomorrow.io, and official NWS/NOAA fog advisories for higher confidence predictions.
  • Email alerts and daily digest — get notified when conditions look promising at your saved locations without having to check every morning.
  • Terrain-aware scoring with support for valley, river, coastal, lowland, and ridge terrain types that influence how fog forms and pools.
  • The algorithm has been through five major versions (v1.0 through v1.5) before this public launch, each refined against real-world fog events in the Pacific Northwest.