About FogWatch
Built for hikers who love the fog
FogWatch started as a personal obsession — a way to know when the marine layer would roll in before driving two hours to a trailhead. It grew into a real-time visibility tracker for the Pacific Coast's most atmospheric hiking areas.
Why we built this
Anyone who's hiked Point Reyes or the Lost Coast knows the feeling: you plan a trip, drive out at dawn, and the fog is either perfect or completely gone. There was no reliable way to know in advance — weather apps give you temperature and rain, not marine layer depth or coastal visibility.
FogWatch pulls real atmospheric data — visibility distance, cloud cover, humidity, and precipitation — and combines them into a single fog score for each hiking area. No guesswork. No driving two hours to find clear skies when you wanted the mist.
We track 12 areas along the Pacific Coast, from the redwood groves of Del Norte County down to the Marin Headlands. Each area updates every 15 minutes using open meteorological data, so the score you see reflects conditions right now.
12
Tracked areas
15m
Refresh rate
4
Data signals
How the fog score works
The visibility score (0–10) is calculated from four real-time atmospheric measurements. A lower score means denser fog.
Visibility distance
40%Raw visibility in meters from the Open-Meteo API. This is the primary signal — direct measurement of how far you can see.
Cloud cover
25%Low cloud cover percentage. High overcast at ground level is the classic marine layer signature along the Pacific Coast.
Relative humidity
20%Humidity above 90% in coastal areas strongly correlates with fog formation. Combined with low temperatures, it's a reliable fog predictor.
Precipitation
15%Light drizzle and fog often arrive together. Precipitation data helps distinguish between fog and rain events.
Score reference
Data source
All atmospheric data comes from Open-Meteo, a free and open-source weather API that aggregates data from national weather services including NOAA, ECMWF, and the German Weather Service. No API key required — the data is publicly available and updated hourly at the source, with FogWatch refreshing every 15 minutes.
Open-Meteo documentationHiking in fog — what you need to know
Fog changes everything on the trail. These guidelines apply to all the areas FogWatch tracks.
Navigation
- Download offline maps before leaving cell range. Apps like AllTrails, Gaia GPS, and CalTopo work without signal.
- Fog can make trail markers invisible at 10 feet. Count your steps between waypoints on unfamiliar trails.
- Carry a compass and know how to use it. GPS can drift in dense tree cover and coastal canyons.
Gear & clothing
- Coastal fog saturates clothing faster than rain. A waterproof shell is non-negotiable, even on warm days.
- Temperatures can drop 15–25°F inside the fog layer compared to inland. Bring an insulating mid-layer.
- Trekking poles help on wet, slippery roots and rocks — common in redwood fog zones.
Timing & planning
- Marine layer typically peaks at dawn and burns off by 11 AM–1 PM. Plan your turnaround accordingly.
- Fog can return quickly in the afternoon, especially in summer. Don't count on the burn-off lasting all day.
- Tell someone your trailhead, route, and expected return time before heading into dense fog conditions.
Coastal hazards
- Sneaker waves are invisible in fog. Stay well back from the surf line on beach sections of the Lost Coast and similar trails.
- Tidal passages on the Lost Coast are only safe at low tide — fog makes it impossible to judge wave timing visually.
- Cliff edges are invisible in dense fog. On headland trails, stay on the marked path and avoid shortcuts.
Ready to track the fog?
Check live conditions for all 12 tracked areas, or set an alert so the fog finds you.