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 Auto-Detect + Easier Override
Adding a location now includes automatic terrain analysis from coordinates, with safer rules that prefer staying on General when signals are weak. You can still override terrain hints at any time.
- New location setup now analyzes terrain in the background and can auto-fill high-confidence hints like coastal, river, valley, and ridge/highland.
- Detection is conservative by design: if confidence is low or mixed, we keep General (auto) instead of forcing a hint.
- Urban handling is now suggestion-first to reduce false positives in smaller towns.
- Existing saved locations can be re-checked from Edit Alert with the Re-detect action, and manual selections always 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.