Marine Weather and Tide Forecast for San Mateo, CA

SHORT TERM
Issued at 1215 PM PDT Thu Sep 10 2026 (This evening through Friday night)

After a warm start to the day, the interior will remain very warm to hot with the ongoing Heat Advisory still in place until 10 PM PDT this evening. However, we are already seeing cooler conditions near the coast as a shallow marine layer is forecast to return as well as an increase in onshore winds.

Tonight, temperatures are forecast to cool into the mid 50s to near 60 deg F near the coast and across the interior valleys.
However, the higher elevations look to only cool into the 70s and potentially the lower 80s. Coastal stratus and/or fog look to develop along the coast and potentially into the North Bay Valleys overnight as the marine layer deepens to around 500 feet.

On Friday, depending on how much stratus/fog develops in the morning, the cooling trend will continue with temperates moderating to near seasonal averages with mostly sunny conditions across the interior. This is a result of the mid/upper level through deepening off of the Pacific Northwest coast and high pressure over the Desert Southwest being suppressed to the south.

LONG TERM
Issued at 1215 PM PDT Thu Sep 10 2026 (Saturday through next Wednesday)

The gradual cooling trend will continue into the weekend as the low pressure off of the Pacific Northwest coast deepens further, bringing rainfall to that region. This will allow the marine layer to deepen as well, reaching around 1500 feet by Saturday night into Sunday. This would also bring increased afternoon and evening winds in the favored valleys, peaks, passes, and gaps.

Beyond this weekend, troughing off of the West Coast looks likely to persist. This will allow for afternoon maximum temperatures to be near to slightly below average and overnight minimum temperatures to be near or slightly above.

AVIATION
(00Z TAFS)
Issued at 428 PM PDT Thu Sep 10 2026

VFR through this evening with gusty onshore flow. Clouds along the coast this afternoon is the return of marine layer. Expect the marine layer to push in tonight and early Friday, but remain compressed. As such, low chc for fog late tonight. Additionally, expect an earlier clearing time on Friday. Overall conf is moderate.

Vicinity of SFO...Breezy NW winds this evening with VFR. Will take some time, but clouds will move through the GG and push through OAK and SFO by Friday AM. MVFR early Friday with clearing during the AM rush.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals.. MVFR/IFR returns early tonight and then lingering through mid morning Friday. VFR Friday afternoon.

MARINE
(Tonight through next Tuesday)
Issued at 428 PM PDT Thu Sep 10 2026

High pressure to north and low pressure to the south will maintain a moderate to fresh northwesterly breeze through Friday, increasing to become fresh to strong this weekend into next week.
Locally hazardous conditions for small craft today will expand to become widespread this weekend into next week. Moderate seas will prevail through the weekend, building to become rough in the outer waters Monday. A longer period southerly swell will mix into the sea state due to tropical systems in the Pacific.

MTR WATCHES/WARNINGS/ADVISORIES
CA...Heat Advisory until 10 PM PDT this evening for CAZ006-502>506- 508>510-512>518-528>530.

PZ...Small Craft Advisory from 3 AM Friday to 3 AM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory from 9 AM to 9 PM PDT Friday for Pigeon Pt to Pt Pinos 0-10 nm.

Small Craft Advisory until 3 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm.