Rain is expected to slide down from the north by late this morning and give a good soaking to the Silicon Valley.
By 9 a.m., the rainstorm had reached San Francisco International Airport. Overnight, and into the morning, higher peaks in Marin County had reported rain levels of up to four inches.
Today is also the heaviest travel day of the holiday season at SFO. An estimated 130,000 passengers are expected to pass through, and more than 2 million holiday travelers are expected to use the airport between today and Jan. 6, SFO spokesman Doug Yakel said.
At the airport, 26 departing flights and 28 arrivals had been cancelled as of 9:30 a.m. Particularly hard hit were passengers expecting to fly on SkyWest Airlines, which cancelled 35 flights according to flightstats.com.
Snow and turbulent winter weather in the Midwest is also causing flights delays between the Bay Area and Chicago, said SFO duty manager Linda Perry.
A high wind advisory is in effect until 10 a.m. with southern winds up to 20 mph.
Rain and thunderstorms are expected to continue tonight with lows expected to be in the lower 50s, and southern winds up to 20 mph.
Rain and possible thunderstorms will stick around on Saturday.
A high surf advisory is in effect until 4 p.m. Saturday.
-Bay City News contributed content to this article.