textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1213 PM PDT Sun Oct 4 2026

- Warm to hot conditions across the region through mid-week

- Hazardous heat conditions expected to persist inland, never leave children or pets in unattended vehicles!

- Elevated fire weather conditions persist in the interior through Thursday

UPDATE

Issued at 1002 PM PDT Sun Oct 4 2026

Despite the hot temperatures across our region today no records were broken this afternoon/evening. The area of high pressure over our area coupled with offshore flow will keep temperatures well above normal through the middle of the week. The Heat Advisory for areas close to the Pacific Coast from Sonoma County to Santa Cruz County has been allowed to expire, however for the Big Sur coastline and the remainder of our interior locations, the Heat Advisory continues through Wednesday. Monday temperatures near the coast will be a few degrees cooler than Sunday, but still above normal, across the interior we'll see temps close to or slightly above what was realized earlier today.

SHORT TERM

Issued at 1213 PM PDT Sun Oct 4 2026 (This evening through Monday night)

It's hot. A persistent ridge over the western United States keeps the area much above the seasonal average (15 to 25 degrees above seasonal average away from the immediate coast). As of 11 AM today temperatures across the region ranged from the 80s into the lower 90s inland, the 70s to the lower 80s close to the Bays, and the middle 60s to the middle 70s for the Pacific coast. There are some high clouds flowing above the SF Bay Area, but they do not seem to be impacting the heat levels. High temperatures today and Monday will be rather similar in the inland valleys, ranging from the middle 90s to near 104. Closer to the Bays, today's highs will be in the middle 80s to the middle 90s while locations along the Pacific coast rise into the 70s. Across the higher elevations and some nearby valleys, especially in the East and South Bays, mild overnight lows in the upper 60s to middle 70s will limit the ability to recover overnight. For Monday, these temperatures are a little uncertain owing to potential impacts from a shallow marine layer or a marginally stronger onshore flow than the current forecast, but highs should remain in the 70s and 80s. If confidence in highs towards the higher part of that range increases, the Heat Advisory for our coastal regions may need to be extended.

Due to the hazardous heat levels, a Heat Advisory is in effect for coastal locations through 10 PM tonight, while inland and Bayshore areas remains under the Advisory through Wednesday. Widespread Moderate HeatRisk blankets the region, corresponding 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. In addition, many of the higher elevations in addition to the East Bay, South Bay, and the Carmel, Hollister, and northern Salinas Valleys see Major HeatRisk, corresponding to a high risk for heat-related illnesses for anyone without hydration or cooling. 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.

LONG TERM

Issued at 1213 PM PDT Sun Oct 4 2026 (Tuesday through next Saturday)

The ridging persists for the next few days and as previously mentioned, the Heat Advisory extends to Wednesday night for the inland and Bayshore regions. Temperatures across the inland valleys remain in the middle 90s to near 105 through Wednesday. Along the Pacific, we continue to monitor how the forecast trends evolve as impacts from a shallow marine layer or stronger onshore flow than the current forecast may significantly impact the immediate coast.

A pattern change will begin Thursday as the ridge flattens and troughing develops in the northeastern Pacific and moves into southwestern Canada and the western United States. This will start a cooling trend with most locations dropping out of Moderate HeatRisk by Friday. Ensemble model cluster analysis hints at significant uncertainty for the upcoming weekend and the early part of the upcoming week regarding the strength of the trough and how long it could persist.

AVIATION

(06Z TAFS) Issued at 944 PM PDT Sun Oct 4 2026

Confidence is mixed as to if stratus/fog will make it to the coastline tonight. Kept the stratus mention in for HAF but confidence is decreasing in fog reaching MRY and SNS. Diurnally breezy winds continue with moderate onshore winds during the day and light, variable winds overnight.

Vicinity of SFO...VFR. Diurnally breezy winds with moderate west to northwest winds around 16 knots expected during the day before winds weaken overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Mixed confidence as to if stratus/fog will reach MRY and SNS tonight. Models are currently overestimating the eastward extent of the offshore stratus (i.e. placing it closer to shore) while observations show the stratus deck to still be well offshore. This is decreasing confidence in CIG development along the Monterey Peninsula. The wrinkle in this, however, is that clear skies across the peninsula will allow for additional radiational cooling and see temperatures dropping closer to the dewpoint. This would increase the likelihood of fog development and LIFR conditions. Leaned towards VFR conditions continuing tonight with some potential for fog to develop early Monday morning.

MARINE

(Tonight through next Saturday) Issued at 944 PM PDT Sun Oct 4 2026

A gentle to moderate breeze and slight to moderate wave heights persist into midweek. Winds increase and wave heights build, seas becoming rough across the outer waters, Friday into the weekend.

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 Wednesday for CAZ503-504-506-508- 510-512>518.

PZ...None.