There are many micro-climates in and around Gualala.....so there is no simple answer.
First, our fog season usually begins end of May to end of June and runs through about September. While others are broiling during peak of summer heat, we are usually cool.
There are offshore wind events with high pressure systems that take away our natural air conditioning, but this usually only lasts for 2 to 5 days before the cool and fog returns.
We can and do have fog other times of the year as well, but not excessively so.
For those usually foggy days in summer, here is what many times will happen: wake up to fog in morning which will burn back to the immediate coast by noontime. Fog may linger there most the rest of the day or it may burn back to a couple miles offshore. Then, about 11 p.m. or so, the fog creeps back in to start the cycle over. This is common, but there are many exceptions as well.