SR-37 Closes for 55 Hours Oct. 23–26 — Detours Between Vallejo and Sonoma

State Route 37 will close in both directions for 55 hours between Mare Island in Vallejo and Sears Point, beginning at 10 p.m. Friday, Oct. 23, and continuing until 5 a.m. Monday, Oct. 26, 2026. Drivers crossing the North Bay should plan for substantial detours and extra travel time.

The closure affects a key connection used by commuters and weekend travelers moving between Solano, Napa and Sonoma counties. Caltrans says the schedule is weather-dependent.

Closure timeline

Wednesday, Oct. 21: westbound SR-37 closed from 7 p.m. to 4 a.m. the next morning.
Thursday, Oct. 22: westbound SR-37 closed from 7 p.m. to 4 a.m. the next morning.
Friday, Oct. 23 through Monday, Oct. 26: both directions closed from 10 p.m. Friday to 5 a.m. Monday.

Before leaving, drivers should check Caltrans QuickMap for current conditions and allow additional time.

Eastbound detour

Eastbound traffic will be directed north on SR-121, right on SR-12/SR-121 (Carneros Highway), right on SR-12/SR-29, and then onto the connector loop back to eastbound SR-37.

Caltrans map of the eastbound SR-37 detour via SR-121, SR-12 and SR-29 during the Oct. 23–26, 2026 closure — Eastbound SR-37 detour. Map: Caltrans District 4.

Westbound detour

Westbound drivers will be directed north on SR-29, west on SR-12 and south on SR-121 before returning to westbound SR-37.

Caltrans map of the westbound SR-37 detour via SR-29, SR-12 and SR-121 during the Oct. 23–26, 2026 closure — Westbound SR-37 detour. Map: Caltrans District 4.

Why the highway is closing

Crews will remove part of the median and place temporary concrete barriers so eastbound and westbound traffic can be shifted onto the westbound side. Sections of the eastbound lanes will then be raised by about three feet to improve flood resilience, including preparation for potential El Niño conditions.

Caltrans has also scheduled a second full closure from 10 p.m. Friday, Nov. 13, to 5 a.m. Sunday, Nov. 15. That schedule may also change because of weather or construction conditions.

Separate SR-37 bridge work: Caltrans has also announced nighttime lane reductions at the Petaluma River Bridge for October 19–24. This bridge rehabilitation is a different project and location from the Mare Island–Sears Point full closure. Drivers whose trips cross both segments should read both advisories and check live conditions.

Travelers using other major Northern California routes can review the separate I-5 Yolo Bypass nighttime closure schedule. Drivers heading toward the coast should also monitor the latest California coastal travel advisories when relevant to their trip.

Official source: Caltrans District 4, published Oct. 13, 2026.