Marine Weather and Tide Forecast for Walnut Creek, CA

SHORT TERM
Issued at 1245 AM PDT Wed Jun 17 2026 (Today and tonight)

A marine layer 1000-1500 feet deep will bring extensive cloud cover to the coast and adjacent valleys this morning. Patchy drizzle has been observed along the coast and will continue through the morning, especially over the higher terrain. By the afternoon, clouds should retreat back to the coastline with mostly sunny skies. The marine influence combined with breezy onshore winds this afternoon will keep areas near the coast relatively cool, with highs mainly in the 60s to lower 70s. Overall, conditions will be very similar to Tuesday. Marine stratus will return tonight, along with patchy drizzle redeveloping along the coast.

High pressure over the area will start to weaken today, which will bring about 2-5 degrees of cooling inland. This will place temperatures near normal for mid June with highs in the upper 70s to lower 90s. Most areas will see Minor HeatRisk today with only isolated pockets in the interior of Moderate HeatRisk. Despite the slight cooling, continue to practice smart heat safety (especially for those more sensitive to the heat) by limiting time outdoors, taking frequent breaks in the shade (if outdoors), and staying hydrated.

Tidal flooding continues across low-lying coastal and Bayshore areas through Thursday morning as high astronomical tides combine with surge effects from wind, swell, and thermal expansion to bring us the highest tides of the summer season. High tides are expected to be 1.7 ft above normal (7.5 ft MLLW) at 12:56 AM early this morning, and 1.2 ft above normal (7.1 ft MLLW) at 1:51 AM on Thursday. In addition, the long-period southerly swell continues, which increases the risk for sneaker waves and strong rip currents, with a Beach Hazards Statement out through Thursday morning. See the BEACHES section for more information, but the main takeaway is to never turn your back to the ocean!

LONG TERM
Issued at 1245 AM PDT Wed Jun 17 2026 (Thursday through Tuesday)

A trough off the coast will approach the area on Thursday and further weaken the ridge. This will continue the cooling trend across inland areas, with highs dropping by around 5 degrees. The trough will begin to move onshore on Friday. Shower and thunderstorm potential associated with the trough will stay primarily over the higher terrain to the north and east of the area as a deep marine layer greatly inhibits any thunderstorm potential. However, there will be enough elevated instability for a 5% chance of thunderstorms across far northern Napa and Sonoma counties Thursday night and Friday with lower chances to the south.

The trough will help to deepen the marine layer Friday into the weekend with breezy onshore afternoon/evening winds. The inland cooling trend will continue with highs Friday and Saturday only reaching the 70s to low 80s at the warmest locations, or about 5 to 15 degrees below normal. Coastal areas will remain relatively cool due to the marine influence. Drizzle may also develop over the coastal waters and along the coast. Troughing will weaken by Sunday with ensembles in agreement that a ridge will rebuild across the West early next week. This will bring a warming trend, especially inland.

AVIATION
(06Z TAFS)
Issued at 958 PM PDT Tue Jun 16 2026

MVFR-IFR stratus is expanding across the region and will impact most of the terminals tonight as breezy onshore winds continue to diminish overnight. Moderate to high confidence that LVK will remain VFR through the night, with some high resolution model output showing stratus impacts in the vicinity of the terminal. Stratus retreats back to the coast Wednesday morning, with the breezy onshore winds resuming in the afternoon, again with a southerly component as a mesoscale low develops off the North Bay coastline.
At HAF, high confidence that ceilings continue through the TAF period. Stratus will begin to expand inland again by the end of the 24-hour TAF period.

Vicinity of SFO... VFR conditions at present with breezy west- northwest winds diminishing through the early overnight hours.
Moderate confidence in MVFR-IFR stratus timing at SFO, but ceilings are expected to develop by 10Z. Stratus will dissipate through Wednesday morning with breezy west winds returning to the terminal in the afternoon. Stratus will return to the terminal area late Wednesday night through early Thursday morning.

SFO Bridge Approach... Stratus may impact the approach path a little later than at the terminal tonight. Otherwise similar to SFO.

Vicinity of OAK and SJC... Stratus has taken hold at OAK with the breezy west winds diminishing through the evening. At SJC, there is low to moderate confidence on the timing of stratus impacts as radiational development is possible, but should no radiative stratus develop, MVFR ceilings should develop around 10-12Z. Stratus will dissipate in the afternoon with breezy northwest winds developing at OAK. Confidence in the wind direction and speed is lower at SJC for Wednesday afternoon as the terminal sits between a northwest flow from SF Bay and downsloping winds from the Santa Cruz Mountains.
Have opted to lean more towards the climatological diurnal wind, but may need to carefully monitor observations and future TAF updates through the day. Stratus will return to OAK sometime late Wednesday night through Thursday morning.

Monterey Bay Terminals... MVFR-IFR stratus through the night into Wednesday morning as breezy winds continue to diminish through the evening and early overnight hours. Stratus should retreat to the immediate coast on Wednesday morning with the breezy onshore winds resuming in the afternoon, coming from the west at MRY and the northwest at SNS. Wednesday evening, stratus flow could impact SNS as early as 00-02Z, and MRY soon after.

MARINE
(Tonight through next Monday)
Issued at 958 PM PDT Tue Jun 16 2026

Fresh to strong north winds across the northern outer waters result in hazardous seas through tomorrow morning. However, onshore pushes will bring moderate to fresh south to southwest winds for the San Pablo and San Francisco Bays during the afternoon and evening hours, as well as near the coast from Point Sur north to Point Pinos and Pigeon Point to the Golden Gate.
Otherwise, generally light to gentle winds into the weekend. Seas will remain slight to moderate into the weekend with a low south- southwesterly swell across most of the coastal waters.

BEACHES
Issued at 1245 AM PDT Wed Jun 17 2026

Long period southerly swell at around 15 to 17 seconds will persist through early Thursday as energetic storms in the Southern Hemisphere continue to affect the California coast, especially for south and southwest facing beaches. Hazardous beach conditions are advertised, specifically for moderate to steeply sloped beaches along the Pacific Coast of the North Bay, San Mateo, Santa Cruz counties. A Beach Hazards Statement for Pacific Coast beaches continues through 5 AM Thursday morning. Be sure to check beach conditions before you head out. Sneaker waves will run up the beach much farther than other waves, potentially catching beachgoers by surprise and resulting in people being swept into the water. Rip currents are strong enough to pull the strongest swimmers away from shore. Swim near a lifeguard if possible. Stay back from the beach, and away from jetties, piers, beachside rocks, and other infrastructure near the water. Never turn your back to the ocean!

MTR WATCHES/WARNINGS/ADVISORIES
CA...Beach Hazards Statement through late Wednesday night for CAZ006- 505-509-529-530.

Coastal Flood Advisory until 5 AM PDT Thursday for CAZ006-506- 508.

Coastal Flood Advisory until 5 AM PDT Wednesday for CAZ505-509- 529-530.

PZ...Small Craft Advisory until 9 AM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM.