Marine Weather and Tide Forecast for Piedmont, CA

SHORT TERM
Issued at 1247 PM PDT Wed Mar 18 2026 (This evening through Thursday)

The strong mid/upper level high pressure, that has resulted in several daily and monthly records the past two days, is currently over southern California and the Desert Southwest. As forecasted, the 500 mb height has strengthened to 594 dam with 850 mb temperatures around 23 degrees C. As such, temperatures this afternoon will warm into the upper 70s along the immediate coastline and into the mid 80s elsewhere closer to the coast. Elsewhere, just inland away from the coast and in the interior, temperatures will rage from the upper 80s to lower 90s and potentially the mid to upper 90s the the warmest interior spots. Some locations along the Sonoma and Marin county coastline remain in the 50s as of early this afternoon as low stratus and a shallow marine layer impacts that region.

Tonight into Thursday morning, expecting the coldest interior locations to cool into the upper 40s (mainly in the North Bay) with low to upper 50s in other valley locations. In the higher elevations across the region, we are only expecting mid 60s to lower 70s.

Thursday, we are expecting a degree or two of warming across the board. Please see the CLIMATE section below for additional details on potential record breaking heat.

LONG TERM
Issued at 121 AM PDT Wed Mar 18 2026 (Thursday through Tuesday)

Rinse and repeat through Friday. Expect record breaking heat each afternoon as the ridge of high pressure stalls over the desert SW.
Confidence is increasing that the heat wave will start to break on Saturday. Our latest forecast has temperatures dropping around 10 degrees on Saturday, and another 5 on Sunday. That would bring us back into the 70s for most inland areas and 60s along the coast to start next week. By the way, that's still 5-15 degrees above normal for this time of year. As the ridge breaks down there is good chance for stronger winds this weekend, which will bring some additional relief to the hot temperatures, but also brings some enhanced fire weather conditions for fine dead fuels. The next chance for any rain is around the end of the month or early April, but the ensemble members diverge spectacularly by that point, and it's just as likely that another dry heatwave moves in.

AVIATION
(18Z TAFS)
Issued at 1003 AM PDT Wed Mar 18 2026

Quiet weather continues with high pressure holding and mainly offshore winds being observed this morning. Diurnally driven onshore winds are expected for areas near the coast or around the Bay later this afternoon and evening and will become offshore or light and variable overnight. VFR conditions will prevail, though there could be some pockets of haze.

Vicinity of SFO...No major changes, light and variable winds, will become onshore this afternoon and evening. Winds may peak at KSFO around 10-15kt after 23Z. Wind weaken late in the evening, with light and variable winds expected overnight and into Thursday morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Quiet weather with offshore flow continuing this morning. Winds will gradually become onshore by the afternoon, with winds becoming weakly offshore or variable by the evening and overnight hours. VFR conditions continue.

MARINE
(Today through Monday)
Issued at 411 AM PDT Wed Mar 18 2026

Moderate northwest breezes persist across the outer waters, with gentle breezes over the inner waters. Strengthening northwest winds and hazardous seas will likely return to the coastal waters late this week and weekend.

CLIMATE
Issued at 421 AM PDT Wed Mar 18 2026

The following are the record high temperatures at the long term sites for March 18th, 19th and 20th.

Location Mar 18 Mar 19 Mar 20

Santa Rosa 84 in 2010 83 in 2004 84 in 2004 San Rafael 80 in 1996 81 in 1964 82 in 1960 Kentfield 89 in 1914 83 in 1996 82 in 2001 Napa 87 in 1914 86 in 1914 86 in 2004 Richmond 78 in 1996 80 in 1996 81 in 2004 Livermore 86 in 2004 82 in 2015 87 in 1915 San Francisco 86 in 1914 80 in 2010 78 in 2004 SFO Airport 77 in 2004 78 in 2010 78 in 2004 Redwood City 84 in 2004 81 in 2010 82 in 2004 Half Moon Bay 75 in 1978 79 in 2010 75 in 2010 Oakland Museum 81 in 2004 81 in 1984 78 in 2001 San Jose 87 in 1914 82 in 1988 78 in 2004 Salinas Airport 84 in 1960 87 in 1997 80 in 1934

The following are the record high temperatures at the long term sites for the entire month of March.

Location

Santa Rosa 91 on March 16, 2004 San Rafael 88 on March 25, 1952 Kentfield 91 on March 28, 1923 Napa 92 on March 17, 1914 Richmond 87 on March 31, 2021 Livermore 90 on March 25 and 26, 2025 San Francisco 87 on March 11, 2005 SFO Airport 85 on March 25, 1952 and March 17, 2026 Redwood City 93 on March 17, 2026 Half Moon Bay 83 on March 31, 2000 and March 17, 2004 Oakland Museum 89 on March 17, 2026 San Jose 89 on March 14, 2015 Salinas Airport 92 on March 14, 2015 and March 17, 2026

MTR WATCHES/WARNINGS/ADVISORIES
CA...Heat Advisory until 8 PM PDT Friday for CAZ006-502>506-508>510- 512>518-528>530.

PZ...None.