Along the coast of central and northern California, prevailing surface winds blow from north to south in the summer and from south to north in the winter. Based on the model, the season when cold coastal upwelling water cools the overlying air to saturation and produces frequent fog is .
[ ]summer
[ ]winter

Summer

Explanation:

Based on the model, the season when cold coastal upwelling water cools the overlying air to saturation and produces frequent fog is in the Summer in California.

It is made to believe that California's coast is produces the most fog worldwide. California has a cold ocean bordered by a pretty warm landmass which produces the best atmosphere for fog. The water along the coast of California is cold because cold water comes from Alaska southward along the coast.

The fog causes cold, someone once famously said that the coldest winter he has experienced was a summer in California.