San Mateo, CA Weather

Key Messages

Updated at 1038 PM PDT Fri Oct 23 2026

- Gusty offshore flow across the North Bay Interior Mountains subsides late this morning

- Near normal temperatures this weekend into the beginning of next week

- Coastal flooding due to astronomical high tides and thermal expansion this weekend through Thursday

Short Term

Issued at 1038 PM PDT Fri Oct 23 2026 (Today and tonight)

Gusty offshore flow across the North Bay Interior Mountains is ongoing tonight, with the windy and dry conditions dropping MinRH values in the 20s for some locations. Fire weather concerns would be higher for this area had we not received the recent wetting rainfall. The offshore flow regime should mostly limit fog development early this morning but still can't be ruled out entirely in some of the river valleys in Sonoma County.

Temperatures today will be around 5 degrees warmer than Friday and near normal for this time of year. The gusty winds across the North Bay will begin to ease by late this morning, with a beautiful day in store area wide across our CWA as upper level ridging builds overhead.

Long Term

Issued at 1038 PM PDT Fri Oct 23 2026 (Sunday through next Friday)

Sunday will almost be a carbon copy of today for the North Bay and Bay Area, with the Central Coast seeing temperatures warm another few degrees. Confidence and consensus in the synoptic pattern is poor after Monday. An upper trough shifts south to our latitude on Monday bringing a return of onshore flow, however the overall progressive pattern is struggling with the depth of the trough and how another system well offshore interacts with the flattening trough as it moves into the Great Basin. Despite the uncertainty in the overall pattern, any troughing or ridging will continue to be progressive and low amplitude, with no large temperature fluctuations or precipitation chances until the end of next week when the NBM seems to pick up on what the current ECMWF deterministic has depicted for next Friday into the weekend, troughing with increasing rain chances.

Aviation

(06Z TAFS) Issued at 827 PM PDT Fri Oct 23 2026

Surface high pressure will build into the Great Basin tonight and Saturday morning. The WMC-SFO pressure gradient will steepen to near 10 mb while the RDD-SAC pressure gradient will steepen to around 3 mb. Offshore winds will develop in response to these gradients, bringing in additional drying tonight and Saturday. Decreasing water vapor will allow nocturnal radiational cooling to steepen and residual humidity in the boundary layer from recent rain may cool to saturation producing patchy low clouds and fog /IFR-LIFR/ tonight and Saturday morning. Radiative cooling will also produce cool air drainage winds to the coastline tonight and Saturday morning. Onshore winds closest to the coast will redevelop Saturday, but not until later in the afternoon. Otherwise VFR is forecast.

Vicinity of SFO...VFR. Northwest wind shifting to light northeast wind by early Saturday morning. West to northwest wind near 10 knots late Saturday afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. West to northwest winds 5 to 10 knots shifting to east to southeast winds 5 to 10 knots tonight and Saturday morning. Northwest winds near 10 knots late Saturday afternoon and early evening.