Most of the microclimates in the Bay Area are disgustingly peaceful, but as the parent notes, there is a distinct lack of seasons (there's approximately two: dry summers, wet "winters") and real weather (I greatly missed thunderstorms when I was there).
A lot of sweaters get sold at Fisherman's Wharf during summer months to people caught unaware.
Local weather is something you experience every day, not something you travel to. Same goes for snow and tahoe.
We lived in the Sunset district which was manageable but later moved to Mill Valley and the summers were _very_ brutal, to me. A couple other office mates lived in San Rafael and I distinctly remember everyone complaining about the heat and sweating.
We all eventually bought air conditioners for our bedrooms just so we could sleep comfortably at night.
But brutal is all a relative term. Someone growing up in the south with no access to AC would not call it brutal while I and my other office mates who were used to AC were "dying" without it
Summers in the bay area are not even remotely brutal.
It tends to be cold, wet, damp, foggy and bone chilling early morning. Not like Winters/Summers in Chicago brutal, but definitely the time I struggle with most (as a new yorker who clearly has to weather acclimated here, I know it sounds ridiculous)