textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1103 AM PDT Wed Sep 23 2026

- Warming trend continues into Thursday bringing pockets of moderate HeatRisk across parts of the Bay Area and Central Coast.

- Cooler conditions arrive Friday into the weekend.

- Near seasonal temperatures early next week.

UPDATE

Issued at 1103 AM PDT Wed Sep 23 2026

The OAK 12Z sounding measured the marine layer around 1400 feet deep this morning, which is roughly 1000 feet shallower compared to yesterday's sounding. This morning, poor humidity recoveries around 20-30% were observed across the Diablo Range, Santa Cruz Mountains, and the Santa Lucia range. Another round of poor humidity recoveries is expected through tomorrow morning. A very weak push of offshore flow will persist through the overnight hours as high pressure continues to build over us, further compressing the marine layer tonight into Thursday morning. While current temperatures are running about 4-6 degrees below the forecast, they are still expected to rise this afternoon as stratus continues to dissipate. Consequently, pockets of moderate HeatRisk will impact the interior East/South Bay and Central Coast valleys as well as the Big Sur coastline into tomorrow. Come early Friday morning, a dry cold frontal passage with a strong onshore push will allow the marine layer to deepen and provide relief with cooler conditions through the weekend.

SHORT TERM

Issued at 1103 PM PDT Tue Sep 22 2026 (Tonight through Thursday)

Marine layer between 1500-2000 feet deep as of Tuesday evening. Low clouds cover areas from Point Reyes southward to Big Sur with a decent push of stratus in SF Bay and the Monterey Bay region including Salinas valley. There is an increasing northerly gradient now to about 5 mb from ACV-SFO that is eroding the stratus from north to south for the North Bay. This is occurring as high pressure is trying to nose into the region from the southwest. 850 mb temps warming to around 20-21 celsius with hot inland temps for the interior Central Coast (90s) with mainly upper 80s to around 90 for the interior North/South/East Bays on Weds afternoon. With persistent onshore winds not really a late September setup where we would expect warm/hot temps at the coast. Looking at the European extreme forecast index we see no areas of interest suggesting this is just a typical warm late Sept day on tap. Models hold onto the warm inland temps for one more day through Thursday. However by Thursday afternoon a storm well to our north will induce a strong onshore/westerly push, ushering in a moderate to strong afternoon/evening seabreeze on Thursday that will signal relief for the Bay Area while the interior Central Coast remains warm/hot through Thursday evening.

LONG TERM

Issued at 1103 PM PDT Tue Sep 22 2026 (Thursday night through next Tuesday)

A fairly well defined early autumn dry cold front passage will push through the region Thursday night into Friday morning. No precip is forecast for the Bay Area as it remains confined to areas north of Cape Mendocino. However, enough cooling and mixing aloft to essentially erode or mix out the marine layer quickly by early Friday morning. Temps still remain seasonably warm/mild Friday but the cooling trend will have begun. Weather this weekend looks nice for the last weekend of September. Certainly no hot weather with inland temps mainly 70s to lower 80s Saturday/Sunday with enough cold air aloft and mixing to keep skies sunny with perhaps only some patchy morning low clouds near the coast and bays.

Early look at next week shows no signal for precip or abnormally hot weather and no fall offshore wind events. Pattern looks pretty zonal suggesting temps running near seasonal norms.

AVIATION

(18Z TAFS) Issued at 1055 AM PDT Wed Sep 23 2026

Mostly VFR currently, the exception is KHAF where LIFR conditions persist. VFR is expected by late morning and will persist until late this evening when sub-MVFR conditions return to the coastal areas. There confidence is moderate for coastal locations to receive sub- IFR and lower confidence for the Bay Area Terminals early Thursday morning. Any low clouds or fog that does develop will clear between 1630Z-1730Z Thursday.

Vicinity of SFO...VFR. Onshore winds are forecast to increase this afternoon, yet no significant gusts expected. Wind speeds ease overnight and into early Thursday morning with a low confidence for sub-MVFR (10-30% probability) yet MVFR is more likely with 20-50% probability at or around 11Z Thursday. Any low clouds that does develop will clear between 1630Z-1730Z Thursday with increasing onshore winds by Thursday afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. Onshore winds are forecast to increase this afternoon before easing after sunset. There is moderate confidence to see similar conditions late this evening and into the overnight as we saw this morning. There is moderate confidence for sub-IFR (30-50% probability) late tonight into Thursday morning before returning to VFR by around 17Z Thursday.

MARINE

(Today through Monday) Issued at 1055 AM PDT Wed Sep 23 2026

Northerly breezes will remain moderate to fresh over the outer waters. Locally hazardous conditions will persist for small craft over the outer waters through Wednesday night. Winds will weaken further across all waters on Thursday. Friday will see an increase in northwest winds accompanied by seas building back up to rough, and continuing into the weekend.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 5 AM PDT early this morning for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 3 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM.