textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1224 PM PDT Thu Oct 1 2026

- Warm to hot temperatures through the next seven days

- Hazardous heat for most inland locations this weekend

- Mild overnight lows in the higher elevations will limit recovery

- Minor coastal flooding at high tide for bayshore locations on the San Francisco, San Pablo, and Monterey Bays through Friday

SHORT TERM

Issued at 1224 PM PDT Thu Oct 1 2026 (This evening through Friday night)

Ridging, ridging, ridging... a basic summary of the weather pattern across the western United States in the short and medium terms. We are in the middle of an extended period of temperatures warmer than seasonal averages and rather compressed marine layers, meaning that the stratus deck will remain confined to the immediate coast during the daytime and expand into the North Bay Valleys, the SF and Monterey Bay regions, and the northern Salinas Valley overnight, but keep the interior valleys generally clear. High temperatures today and Friday range from the middle 80s to middle 90s inland, the upper 90s across the warmest spots of the interior Central Coast, the middle 70s to middle 80s near the Bays, and the middle 60s to lower 70s at the Pacific coast. The onshore breeze will be rather light with gusts of 20 to 25 mph possible through favored gaps and passes and the northern Salinas Valley in the afternoon and evening hours.

Regions of Moderate HeatRisk are expanding across the inland regions today and Friday. These correspond to a moderate risk of heat- related illnesses for sensitive populations, including children, the elderly, pregnant women, people with chronic illnesses, and people who work or live outdoors without access to adequate cooling or hydration. Follow these tips to avoid heat exhaustion and heatstroke:

* Stay hydrated and drink plenty of fluids. * Wear lightweight, light-colored clothing. * Reduce time spent outdoors or stay in the shade. * Never leave people or pets unattended in vehicles. * Use sunscreen if going to the coast or the pool.

Minor coastal flooding is possible across the bayshore locations of San Francisco Bay, San Pablo Bay, and Monterey Bay around high tide. Up to 1.1 feet of inundation above normally dry land is expected, including up to 0.7 ft of surge caused by thermal expansion and sea level rise since the sea level datum (basically the point where we define as "sea level") was set in the 1983-2001 period. At the San Francisco tidal gauge, high tide is expected to be 1.1 ft above normal (6.92 ft MLLW) at 2:58 PM on Thursday 10/1 and 0.9 ft above normal (6.71 ft MLLW) at 3:58 PM on Friday 10/2.

LONG TERM

Issued at 1224 PM PDT Thu Oct 1 2026 (Saturday through next Wednesday)

As the upper level ridge starts to amplify over the western United States, a noticeable warmup this weekend will cause inland highs to rise into the middle 90s to near 103, while the Bays see highs across the 80s to the lower 90s, creating hazardous heat conditions for anyone without adequate cooling or hydration. Mild overnight lows in the upper 60s to middle 70s across the higher elevations and the middle to upper 60s in the interior East and South Bays will limit the opportunity for the body to recover overnight. As a result, a Heat Advisory has been issued from 11 AM Saturday to 10 PM Sunday across the Sonoma Coastal Range, the North Bay Interior Mountains, the San Francisco Bay Shoreline, the East Bay and South Bay, the Santa Cruz Mountains, the Santa Lucia Range, the interior mountains of Monterey and San Benito Counties, and the southern Salinas Valley. Meanwhile, locations along the Pacific Coast will feel the influence of a highly compressed marine layer, with highs in the upper 60s to middle 70s and lows in the upper 50s to lower 60s.

Towards the beginning of the next work week, the ridge begins to flatten and temperatures may cool by a couple of degrees, but chances for hazardous heat remain high and the Heat Advisory may A slight cooling of a couple of degrees at most is possible towards the next work week as the ridge begins to flatten, but need to be extended as the forecast comes into better view. Ensemble model cluster analysis converges on another amplification of the ridge towards the later part of the next work week, and things get interesting again for the second weekend of October (the 10th and 11th). The clusters begin to split into scenarios that keep the ridging in place over the western United States and those that show more zonal flow or even a trough coming into the West Coast. This split between the cluster scenarios will be interesting to look at through the week, and is part of the reason why forecasts beyond the next seven days are more often discussed in terms of probabilities than deterministic language.

AVIATION

(06Z TAFS) Issued at 929 PM PDT Thu Oct 1 2026

The stratus is rolling in, bringing IFR to LIFR conditions to the coastal terminals. These clouds will continue to push inland through the night, impacting all but the most inland terminals. Clearing times will be similar to Thursday morning, roughly 17-18Z.

Vicinity of SFO...High clouds are obscuring the current extent of the stratus on the satellite image, but Half Moon Bay is reporting 300 foot ceilings for what it's worth. The probability of IFR ceilings reaching SFO has increased to 50-70 percent with the best window between 12Z and 15Z. If these ceilings do reach the terminal, they should quickly clear through the late morning.

SFO Bridge Approach...This is the type of shallow marine layer set up where the approach could get ceilings a couple hours earlier than the terminal as the stratus moves in through the Golden Gate and swirls around the SF Bay before reaching SFO.

Monterey Bay Terminals...IFR-LIFR ceilings are firmly in place at both SNS and MRY and are very unlikely to improve over the next 12 hours. In fact there is a decent chance for fog at both terminals through the early morning.

MARINE

(Tonight through next Wednesday) Issued at 929 PM PDT Thu Oct 1 2026

A gentle to moderate northerly breeze will continue through the weekend and into next week.

FIRE WEATHER

Issued at 1224 PM PDT Thu Oct 1 2026

Persistent ridging across the western United States leaves the interior hot and dry with poor to very poor daytime humidity retention away from the immediate coast, while a compressed marine layer leaves overnight humidity recoveries poor across the higher elevations. Hot daytime temperatures and mild overnight lows in the thermal belts pose hazards for fire crews working in high elevation areas, particularly within the Timber Fire where Major to Extreme HeatRisk is possible during the weekend. In addition, the hot and dry conditions lead to rising ERC values with values in the North Bay and interior Central Coast expected to reach the 90th to 97th percentile next week.

DialH

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until 6 PM PDT Friday for CAZ006-506-508- 529-530.

Heat Advisory from 11 AM Saturday to 10 PM PDT Sunday for CAZ503- 504-508-510-512>518.

PZ...None.