What is the climate of California in late September?

Question

Is it humid? Or is it starting to get cold?

Answer 1

I'll answer for Southern California (I actually don't think Northern California is that different).  The weather is usually warm to hot, and quite dry.  Summer thunderstorms over the mountains usually end by the first week in September, and not long after that the Santa Anas start.  These hot, dry northeasterly winds can often bring the hottest temperatures of the year to the coastal sections.  San Diego's all-time hottest temperature, 111 F, occurred on September 26, 1963.

Occasionally a dying tropical storm can flood the area with warm, humid air and produce September's rare rainfall, but the month is usually among the sunniest of the year.

Answer 2

Northern California is usually warm and dry in late September. Overnight lows are generally in the 50's, but daytime temperatures away from the coast are still in the 80's and 90's. Near the coast, in places like Monterey and San Francisco, September is the warmest month of the year, with average highs around 70.

Answer 3

WHERE in California?!?

It's a big state with just about every type of climate. The climates vary widely.