Marine Weather and Tide Forecast for Hercules, CA

SHORT TERM
Issued at 935 PM PDT Sat Apr 18 2026 (Tonight through Monday)

Satellite imagery shows high clouds continuing to cover the Bay Area and Central Coast tonight, which are expected to continue to push through the region in the overnight period before steadily thinning and scattering Sunday morning. Low temperatures tonight are expected to hover in the middle 40s to lower 50s across the region, perhaps a few degrees warmer than the current forecast if the high level cloud cover is enough to inhibit radiational cooling and reflect thermal energy back to the surface.

Today will be a day of temperatures close to the seasonal averages, with the inland valleys reaching highs in the 70s, the Bays seeing highs in the middle 60s to lower 70s, and the Pacific coast hovering around the upper 50s to the lower 60s. A gentle onshore breeze with a southwesterly component will develop during the afternoon, with the breezy winds persisting into the night as a cold front approaches the region.

LONG TERM
Issued at 935 PM PDT Sat Apr 18 2026 (Monday night through next Saturday)

The focus of the seven-day outlook continues to be centered around the cold front coming through the Bay Area and Central Coast for the early part of the work week. Pre-frontal rain showers are expected to arrive sometime Monday morning across the North Bay and continue to spread southward through the day, with the main frontal band coming through later on Monday into Tuesday morning. Behind the front, and with the associated upper level low coming through northern California, the newly arrived cold pool will allow for a chance of isolated to scattered thunderstorms through Tuesday afternoon and evening, with probabilities ranging from around 20 to 30 percent across the region. Lingering showers and chances for isolated thunderstorms (up to 15% probability) continue through Wednesday, and should move out of the region by Wednesday night.
Through all of this, high temperatures will dip into the lower to middle 60s in the lower elevations to the 50s across the higher elevations, and rain totals will range from 0.5-1.5" across the interior valleys and most of the Bay Area and Monterey Bay regions, to around 1.5-3" in the coastal ranges and the interior mountains of the North Bay. This should be mostly beneficial across the region, but some minor nuisance flooding is possible in urban and poor drainage areas if heavy rain showers or thunderstorms develop.

As the frontal system passes, temperatures will warm slightly into a rather dry latter part of the week, back to around the seasonal averages rather similar to today's highs. Extended guidance from the Climate Prediction Center leans towards temperatures and rain totals above seasonal averages for the last week of April.

AVIATION
(06Z TAFS)
Issued at 935 PM PDT Sat Apr 18 2026

Broken to overcast high clouds continue and will persist through the TAF period. A slow moving cold front over the Eastern Pacific will gradually slide towards the coast over the next couple days.
This will gradually shift winds to a southerly direction and eventually bring some rain and widespread mid-level ceilings. In the meantime there is a decent chance for marine layer stratus to creep in overnight, particularly at STS, HAF, MRY and SNS. While not in the TAF explicitly, SFO, OAK, and SJC have a slight chance of a sunrise stratus surprise as well.

Vicinity of SFO...IFR ceilings just formed at HAF, but they will likely struggle to cross the Peninsula overnight. That being said, there is 20-30% chance of MVFR ceilings between 13-17Z. As the cold front approaches, winds will tend to be just south of west Sunday afternoon, rather than the typical WNW.

SFO Bridge Approach...Persistent high clouds similar to SFO.

Monterey Bay Terminals...The southern terminals have the best chance for ceiling impacts Sunday morning with more low level moisture already in place.

MARINE
(Tonight through next Friday)
Issued at 935 PM PDT Sat Apr 18 2026

A slow moving cold front will approach the coast through Monday, gradually flipping the wind direction southerly over the next 24 hours before increasing to a fresh breeze Sunday night through Monday as some rain moves in. After the front passes, the associated low pressure system will move through the coastal waters, bringing a slight chance for thunderstorms on Tuesday.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory from 9 AM to 3 PM PDT Monday for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory from 3 AM to 3 PM PDT Monday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.