textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1216 AM PDT Sun Oct 4 2026

- Moderate to major HeatRisk across the Bay Area and Central Coast Sunday

- Moderate to major HeatRisk across the interior Bay Area and Central Coast Monday through Thursday

- Elevated fire weather conditions across the higher terrain through Thursday

SHORT TERM

Issued at 1216 AM PDT Sun Oct 4 2026 (Today and tonight)

The 00Z sounding observed the second hottest 850 mb temperature for the date and time at 24.35 degrees Celsius; however, no daily maximum temperature records were broken. The Heat Advisory has been extended in area to now include all of the Bay Area and Central Coast through 10 PM Sunday. Locations along the immediate coast may have relatively cooler conditions; however, weaker than normal onshore flow will limit relief even just a couple miles inland. Temperatures 10 to 20 degrees above normal and weaker than normal onshore flow will limit overnight relief, resulting in moderate to major HeatRisk. Across the higher terrain, elevated fire weather conditions continue from hot and dry conditions with even less relief, prominent thermal belting, and prolonged burn periods. Fog is expected to develop around the Monterey Bay tonight with lower confidence for other locations along the Pacific Coast. Subsidence aloft will support a compressed and shallow marine layer that will mix out shortly after sunrise, providing another nudge that even the coast will got hot.

LONG TERM

Issued at 1216 AM PDT Sun Oct 4 2026 (Monday through Saturday)

There will be subtle fluctuations Monday through Wednesday; nonetheless, upper-level ridging will prevail. The Heat Advisory will remain in effect through 10 PM Wednesday for most of the interior Bay Area and Central Coast as temperatures 10 to 20 degrees above normal bring moderate to major HeatRisk. The Marin Hills, Northern Monterey Bay, and Northern Salinas Valley (including Carmel Valley and Hollister Valley) may need to be grouped in as well with similar conditions and high probabilities for moderate to major HeatRisk. San Francisco will also remain a contender with 60%+ probability for the eastern half of the city to reach 80 degrees Monday and Tuesday with probabilities dropping below 60% by Wednesday except for the far southeastern part of the city. Moderate HeatRisk will persist into Thursday across the interior with areas of major HeatRisk across the North Bay Interior Mountains, Interior East Bay, Santa Cruz Mountains, and Santa Lucia Mountains. Elevated fire weather conditions will continue through Thursday across the higher terrain from the hot and dry conditions. Global ensemble clusters show signs of the upper-level ridge weakening Thursday with troughing off the West Coast likely (80% chance) by Saturday. As a result, HeatRisk will drop below hazardous levels Friday with temperatures moderating to near to slightly below normal by Saturday. It's at the tail end and beyond the long term forecast, but something to watch will be if the aforementioned trough brings remnant tropical moisture from Hurricane Rachel.

AVIATION

(12Z TAFS) Issued at 415 AM PDT Sun Oct 4 2026

Strong high pressure aloft is compressing the marine layer to 500 feet or less. A patch or two of fog /LIFR/ are possible this morning otherwise VFR is forecast during the 12z TAFs.

Vicinity of SFO...VFR. Mainly west wind 5 to 15 knots.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. East to southeast cool air drainage winds 5 to 10 knots in the morning, becoming onshore 5 to 10 knots in the afternoon. East to southeast winds 5 to 10 knots late tonight and Monday morning.

MARINE

(Today through Friday) Issued at 201 AM PDT Sun Oct 4 2026

A gentle to moderate NW breeze and moderate wave heights will prevail for the next several days.

FIRE WEATHER

Issued at 405 AM PDT Sun Oct 4 2026

Hot and dry conditions will continue through Thursday, which will be accompanied with weak offshore flow. Poor to very poor overnight recovery is expected for the thermal belts, generally for elevations above 1000-1500 feet, leading to elevated fire weather conditions. The marine layer is expected to be confined to the immediate coast and around 500 feet. If working in the thermal belts, Moderate to Extreme HeatRisk is forecast this week, with temperature and HeatRisk trends improving late week. A pattern change is expected late in the week or over the weekend. Cooler weather and the potential for improved RH recovery is forecast or Friday.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Heat Advisory until 10 PM PDT this evening for CAZ006-502-505- 509-528>530.

Heat Advisory until 10 PM PDT Wednesday for CAZ503-504-506-508- 510-512>518.

PZ...None.