Why fog is hard to predict
Humidity alone isn't enough. Wind alone isn't enough. Cloud cover alone isn't enough. Photogenic valley fog requires several conditions to line up at once, and most weather apps don't read them together.
Dew Point Depression
When air temperature and dew point converge below 2°C, the air is near saturation. This is the single strongest fog predictor and the first thing FogCast checks.
Wind Speed
Fog needs calm air. Below 5 km/h is ideal. Above 15 km/h, fog disperses before it can pool in the valley. A standard weather app won't flag this combination.
Overnight Sky Clarity
Clear overnight skies let the ground cool rapidly, pushing surface temperatures toward the dew point. Counterintuitively, clouds overnight suppress radiation fog.
Temperature Trend
FogCast reads the overnight temperature arc. If temps are converging toward the dew point hour by hour, fog probability increases significantly by pre-dawn.
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Set a FogCast threshold once. The app will alert you when conditions at your saved locations look promising, so you're not manually checking at 4am.
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Fog photography at Blue Ridge Parkway
The Blue Ridge Parkway runs 755 kilometers along the spine of the Appalachian Mountains, passing through some of the most fog-prone terrain in the eastern US. The elevated ridgeline position means the parkway sits at or above the fog ceiling on many mornings, with layered valley fog visible from dozens of overlooks between Virginia and North Carolina.
The most photographed fog overlooks include Rough Ridge, Waterrock Knob, and the Linn Cove Viaduct section near Grandfather Mountain. At these elevations, fog typically sits in the valleys below while the parkway itself is clear, producing the classic "sea of clouds" compositions that define Blue Ridge fog photography.
Fall is peak season, running from mid-October through early November when foliage and fog combine. Spring is the second most reliable window. Fog forms overnight as cold air drains into the valleys and is usually most dense in the hour before and after sunrise.
Frequently asked
Can I check FogCast on the website?
This page shows a preview of current conditions, including humidity, wind, temperature, and dew point. The full FogCast score, 7-day outlook, push notifications, and best shooting windows are available exclusively in the LightCast app for iOS.
Is FogCast free?
The current conditions preview on this page is free, no account needed. The full FogCast tool is in the LightCast Suite iOS app, which includes a 7-day free trial. After the trial it's $2.99/month, cancel anytime in the App Store.
Why use FogCast instead of checking humidity?
Humidity alone doesn't tell you whether photogenic fog is likely. High humidity with strong wind produces no fog at all. FogCast combines dew point depression, wind speed, overnight sky clarity, temperature trend, and visibility into a single score built specifically for fog photography planning.
What is FogCast's scoring scale?
FogCast scores fog conditions from 0 to 100. A score of 75 or above indicates dense fog is expected. 55 to 74 means fog is likely and worth chasing. 35 to 54 suggests patchy mist is possible. Below 35, conditions are unlikely to produce photogenic fog. The full score is available in the LightCast app.
