A summer-sized ridge of high pressure will bring offshore winds that will act a bit like an atmospheric hair dryer across the Bay Area on Friday, even to the coastline.
Even though October is usually a warm month in San Francisco, it's unseasonably warm in other cities, including at the normally cooler cities by the ocean.
So why is it so warm and dry this late in the year?
Underneath a strong ridge of high pressure, air is forced downward, compressing the air that in turn warms and dries it all the way down to sea level.
Highs will soar into the mid 80s to upper 90s from Pacifica to Pleasanton with similar temps expected into Saturday. For the coastal communities hitting the 90s, temps will likely break a few records and possibly again for Saturday.
The Bay Area's hot weather pattern will also contribute to air quality issues with a Spare the Air day for Friday. The highest levels of air pollution will likely be over the South Bay and Santa Clara valley with commuters urged to use mass transit or limit driving until our onshore, cooling winds return.
Starting Sunday the return of onshore winds are expected, which should begin to cool down the coastline and eventually inner bay locations by Monday.
It's even hotter in Southern California, where Los Angelenos are preparing for a sweltering weekend marked by Santa Ana winds and extreme fire danger. New highs for the date were set Thursday in Long Beach, Oxnard, Santa Barbara and Santa Maria. Temperatures hit the mid- to high 90s across Southern California. Downtown Los Angeles reached 96 degrees -- not a record, but still above normal for October.
NBC LA's Jonathan Lloyd contributed to this report.
