Fog Forecast for Mount Shasta

Mount Shasta is an isolated 4,322-meter stratovolcano in northern California that rises dramatically from the surrounding valley floor, visible for over 150 kilometers on clear days. The Shasta Valley to the north and the wide flats of the upper Sacramento River watershed to the south are both prone to radiation fog in autumn and winter, and when valley fog fills to the 1,500-meter level and only the upper cone of Shasta is visible above, the effect of the volcano emerging from a white sea is extraordinary.

The most reliable fog photography positions are on Highway 89 north of McCloud and the roads above the valley floor on the mountain's lower slopes, where elevation gives a perspective above the fog layer. When the Shasta Valley fog is at its densest, the forested lower slopes disappear and only the snowcapped upper mountain is visible. October through December is the strongest fog season as the Sacramento Valley fog machine begins operating and northern California valleys fill with tule fog.

Mount Shasta fog is primarily tule-type valley fog — the same radiation fog that blankets the Central Valley — pushing north into the Shasta Valley basin under stable high-pressure conditions. Clear, cold nights following wet periods are the best trigger. If dew point depression is under 2°C by midnight with calm winds, the valley floors around Shasta are likely to fill with dense fog by 4 to 5am.

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.