A recent photo went viral on social media that showed a rare fog descending on the Sacramento skies. Here, the skyline of the city was clearly engulfed under the fog and this was in sight for miles. While Sacramento may not have the best air quality in the world, it’s hardly at San Francisco levels.

The image below was originally uploaded to Reddit by a confused local who asked about its origins, having claimed to never have seen anything like it before.

It turns out that this is actually called tule fog which is somewhat local to the area. Despite this, it’s not exactly very common either and can even cause harsh driving conditions.

Tule fog is a type of dense ground-level fog that is particularly common in the Central Valley of California It is named after the tule grass wetlands found in the region. Tule fog typically occurs during the fall and winter months, and it is known for its thickness and persistence.

This type of fog is caused by specific meteorological conditions. It usually forms when there is a combination of cool, moist air from the Pacific Ocean, which moves inland, and cold air trapped near the surface in the Central Valley. When these conditions meet, the moisture in the air condenses into tiny water droplets, creating thick fog that can reduce visibility to near zero.