That 'splains it.

Men without jackets and women fanning themselves . It was easily 85 degrees. Our usual warm spell is a month late!

the central valley stops getting so damn hot like in the summer months.

When that happens the usual cold air coming from the pacific streaming across San Francisco to the central valley stops... and sometimes reverses from the east bay hills and compresses on it's way to the Pacific... which heats the air.

October is when the east bay hills are at the the greatest danger of fire. Hot dry winds from the east...

Summer in the city is usually cool to actually cold... as Mark Twain once observed: "The coldest winter I ever spent was the summer I spent in San Francisco".

You can always tell the tourists from the locals. In the summer the locals are wearing many layers including a zip up hoodie or similar and the tourists are freezing their chi-chis off in T-shirts and shorts. In October the locals are now breaking out the T-shirts and shorts... but have a back up of pants and wind breaker in case the winds shift.


the Oakland Hills fire in 1991 was a prime example of this weather pattern- Oct 23rd I think.

They usually schedule "fleet week" in October (this week was fleet week) for the same reason.