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Highway 37 Closes for 55 Hours This Weekend: Your Guide to the Wine Country Gateway Drive

Cars and trucks driving Highway 37 across the wetlands at the north end of San Pablo Bay, with open water on one side and marsh on the other

Introduction: The Low Road Into Wine Country Goes Dark

Highway 37 slips out of Vallejo, drops onto a low causeway, and runs for miles with water on one side, marsh on the other, and nothing between your tires and San Pablo Bay except a narrow strip of asphalt. It is the main route into Sonoma from Vallejo, the East Bay, and Interstate 80, under wine country weekends, Sonoma Raceway days, and North Bay commutes alike. This week, it closes.

Westbound Highway 37 shuts tonight, Thursday, October 22, from 7 p.m. to 4 a.m. Then the big one: a full closure in both directions, from 10 p.m. Friday, October 23, through 5 a.m. Monday, October 26, between Mare Island in Vallejo and Sears Point in Sonoma County. If Sonoma, Napa, or the North Bay is in your weekend plans, this closure is now the most important part of them.

What Happened: El Niño Prep, a Demolished Median, and a Road Raised Three Feet

This is not a crash closure. It is a deliberate, expedited shutdown to get ahead of the water. Caltrans District 4 says the work is emergency preparedness for El Niño storms, on a corridor with a long flooding record. The agency's reminder on the 55-hour closure, published October 19, lays out the sequence: westbound-only overnight closures on Wednesday, October 21, and Thursday, October 22, from 7 p.m. to 4 a.m., then the full closure starting Friday night.

During the weekend shutdown, crews will demolish the median and install K-rail barriers to shift both eastbound and westbound traffic onto the current westbound lanes. Once traffic is shifted, the real project starts on the eastbound side: raising portions of the roadway by about three feet to improve resiliency and address the flooding that repeatedly closes this low stretch. All of the work is weather dependent, and Caltrans warns that additional weeknight work may follow.

One more date: secondary overnight closures are scheduled from Friday, November 13, at 10 p.m. through Sunday, November 15, at 5 a.m., to move the temporary barrier to the eastbound side. The City of Sonoma's closure notice warns travelers to expect significantly longer trips, with detour traffic spilling onto other Sonoma Valley routes all weekend.

The detour itself is simple on a map and slow in real life. Eastbound drivers leave Highway 37 for northbound State Route 121, continue on State Route 12, the Carneros Highway, then use State Route 29 to rejoin eastbound 37. Westbound drivers do the reverse: northbound 29, westbound 12, then southbound 121 back to westbound 37. Caltrans is direct about the result: expect significant delays, use alternate routes when you can, and follow the posted signs rather than improvising through the marsh roads.

The Drive: Vallejo to Novato, 21 Miles Across the Top of the Bay

When open, Highway 37 is a 21-mile run along the northern shore of San Pablo Bay, from Interstate 80 in Vallejo west to U.S. Highway 101 in Novato. Its appeal is exposure: a flat causeway across wetlands, sloughs, and tidal marsh, with big sky, bird-filled water, and the Sonoma hills rising ahead. On a clear morning it feels like driving across the bay itself.

Drive it with these stops and landmarks in mind, westbound from Vallejo:

  • Mare Island Strait and the Napa River crossing — the eastern gateway and edge of the closure zone, where the road leaves Vallejo and commits to the causeway.
  • The marsh causeway — the heart of the drive. Tidal water, restored wetlands, and working sloughs run right up to the shoulder. Pull off only at legal turnouts; much of this road has no real shoulder to spare.
  • Sears Point and State Route 121 — the junction where wine country traffic turns north toward Sonoma and the Carneros wine region. Sonoma Raceway sits in the hills right at this corner, which is why race weekends hit this road harder than almost anything else.
  • The Petaluma River and Novato — the western end, where the causeway gives way to Marin and the junction with Highway 101. From here, the Golden Gate Bridge drive south into San Francisco is the natural onward leg.

This weekend the detour is the drive. The SR-121 and SR-12 route through Carneros is genuinely pretty: low vineyard hills, pasture, and two-lane wine country road instead of marsh causeway. It will be crowded, so treat it as a scenic route under load, not a shortcut. For what is open in Sonoma this weekend, start with Sonoma County's official visitor site.

Practical Tips: Driving It This Weekend

  1. Do not plan a Friday night or weekend crossing on Highway 37. It is fully closed from 10 p.m. Friday, October 23, to 5 a.m. Monday, October 26, between Mare Island and Sears Point. There is no partial opening and no local-traffic exception in the Caltrans notice.
  2. Tonight counts too. Westbound Highway 37 closes Thursday, October 22, from 7 p.m. to 4 a.m. An evening trip west toward Novato or Highway 101 needs the detour, or an earlier start.
  3. Use the posted Carneros detour, not a maps-app invention. Routes 121, 12, and 29 are the signed detour in both directions. The marsh and farm roads around the bay are narrow, dark, and not built for freeway volume.
  4. Budget the delay Caltrans is warning about. Officials expect significant delays and longer travel times, with extra traffic spilling onto other Sonoma Valley routes. Add at least an hour to a Vallejo to Sonoma trip this weekend, and more around peak wine country hours.
  5. Check conditions the morning you go, and again before returning. Caltrans QuickMap carries live closures and message signs, and 511 Bay Area carries regional updates. All of this work is weather dependent, so times can move.
  6. Remember November 13 to 15. A second round of overnight closures is already scheduled to move the temporary barriers. If you drive this corridor regularly, put it on the calendar now instead of rediscovering it at the gate.

When to Go

For a pleasure drive, wait for a clear weekday after the road reopens on Monday morning, October 26, and go early. Morning light on the marsh, birds working the shallows, and thin traffic is Highway 37 at its best. Fall adds harvest time in Carneros and Sonoma, and migratory birds arriving on the bay.

Avoid race days at Sonoma Raceway for the relaxed version, and avoid heavy rain until the raising work is done. A strong storm can still close this road on short notice. That vulnerability is also what makes it worth driving deliberately, the same quality that makes Highway 1 through Big Sur essential California: a road held in place against a moving coast.

The Bottom Line

Highway 37 is closing this weekend so it can keep working this winter. Plan around it, then come back and drive the causeway properly: water on both sides, wine country ahead, and one of California's most quietly dramatic roads under you.

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