A large ridge of high pressure across the West is producing warmer than average daytime highs across the interior. It is also driving some east-west mid-level flow. This steering flow is carrying subtropical (muggy) air across the area. For most of the Central Coast the main impact will be high level clouds and some increase in the humidity. This is most pronounced across southern SB county but is also creeping into SLO county.
There is a slight chance of thunderstorms but primarily over the upper elevations of SB county, also some stray cells could produce sprinkles essentially anywhere. Since thunderstorms are possible dry lightning is a concern and a fire weather threat. The chances of any of that is about 10-20% so most folks will not see a major impact.
Outside of that the thing to watch will be temperatures inland for the Mid-State Fair. Some filtering of high clouds and more SW breeze late in the day should keep temps under 100 for the balance for the week (but still in the mid 90s). Early next week the ridge shifts positions and should allow temps in the 100-107 range Monday thru Wednesday.
At the coast, beaches are dealing with night and morning marine clouds however high clouds could interrupt the deck over the next several days which should lead to at least some coastal warming. Most beaches in the 70s but Morro Bay should stay in the Mid-60s with Pismo Beach near 70. Coastal valleys will be in the mid 70s to lower 80s thru the weekend. Early next week these temps will also jump with the expanding high pressure.