Marine Weather and Tide Forecast for Petaluma, CA

SHORT TERM
Issued at 132 PM PDT Thu Oct 15 2026 (This evening through Friday night)

Another warm and sunny day across our area with offshore flow providing above normal temperatures and abundant sunshine. With an upper level ridge over NorCal and upper level low over SoCal, we're seeing a common setup for a relatively weak Diablo wind event through the North Bay interior mountains, which has resulted in a Red Flag Warning issued for 10p tonight through 11am Friday for that area. The highest peaks around Mt St Helena have already seen gusts between 50-60 mph and we expect that to continue until winds at lower altitude begin to increase later tonight through late morning Friday. It hasn't rained in that part of the North Bay since September 4th, so conditions and fuels are very dry (see the Long Term discussion below for how that may change next week).
Elevated fire weather concerns extend beyond the Red Flag Warning so we continue to message to abstain from any activities that could ignite a wildfire. The offshore flow continues to work against marine layer development with some of our coastal locations like Half Moon Bay and Monterey already in the low 80s and representing some of our highest temperatures of the day so far.

The offshore flow will continue tonight providing clear skies area wide. Thermal belting above 1000ft over much of our area will result in poor RH recovery and overnight lows well above normal, providing little relief from the heat until at Saturday night.

LONG TERM
Issued at 132 PM PDT Thu Oct 15 2026 (Saturday through next Wednesday)

We expect the Red Flag warning over the North Bay interior mountains to expire at 11am Friday with easing winds as the mitigating factor, temperatures will remain warm with very dry conditions and fuels persisting through Saturday until a notable pattern change sets in on Sunday.

An upper level trough to our north will approach the coast over the weekend bringing a return of onshore flow, a subsequent cold front and notably cooler temperature and multiple days through the middle of next week with scattered light rain chances. We're not expecting any one location to see more than a 0.25", and most locations that see some rain will get less than a 0.10" but confidence is increasing that most of our area will see at least a little bit of rainfall, with exact timing still too far out to speak of with any confidence.

AVIATION
(00Z TAFS)
Issued at 433 PM PDT Thu Oct 15 2026

VFR through the forecast period due to offshore flow and dry air.
Biggest challenge aviation wise will be dialing the winds. At points winds will be relatively light and variable. Offshore flow will strongest over the N and E Bays. Didn't include in the TAF for STS/OAK, but marginal (20-30% chc) of LLWS. LLWS most likely from 08-15Z.

Vicinity of SFO...VFR. Offshore push for the Friday AM rush.
Onshore heading into the Friday afternoon rush.

SFO Bridge Approach...VFR.

Monterey Bay Terminals...VFR.

MARINE
(Today through Tuesday)
Issued at 1047 AM PDT Thu Oct 15 2026

Moderate seas prevail across the outer waters, while the inner waters experience slight to moderate seas through Friday night.
During this time frame, gentle to fresh northerly breezes continue. Moderate to fresh northerly winds return for the weekend, which will be accompanied with rough seas.

FIRE WEATHER
Issued at 132 PM PDT Thu Oct 15 2026

A Red Flag Warning was issued for the North Bay Interior Mountains that goes into effect at 10PM tonight and runs through 11AM Friday morning. This is due to moderate offshore winds very dry with very poor overnight humidity recoveries only reaching 15 to 25 percent. Rapid fire spread is possible given the combination of gusty northerly winds and very dry overnight conditions.

Elsewhere in the Bay Area, elevated to near critical fire weather conditions continue for the higher elevations late tonight through Friday morning. Dry conditions, poor overnight RH recovery, combined with the breezy winds, warmer weather, and available fuels leads to the elevated to near critical fire weather conditions.

MTR WATCHES/WARNINGS/ADVISORIES
CA...Red Flag Warning from 10 PM this evening to 11 AM PDT Friday for CAZ504.

PZ...None.