State Route 37 is fully closed in both directions between Mare Island in Vallejo and Sears Point in Sonoma County from 10 p.m. Friday, Oct. 23, until 5 a.m. Monday, Oct. 26, Caltrans says.

Why it matters: SR-37 is a main link between Solano, Napa, Sonoma and Marin counties. The California Highway Patrol warns of significant delays, especially on detours through Napa County, ABC10 reported.

What crews are doing

As part of El Niño storm preparation, crews are removing the median and installing k-rail to shift both directions into the westbound lanes. They will then raise parts of the eastbound lanes by 3 feet to reduce flooding, Caltrans said.

Detours

  • Eastbound: Take northbound SR-121 in Sonoma, then SR-12 (Carneros Highway), then SR-12/SR-29, and use the connector loop back to eastbound SR-37.
  • Westbound: Take northbound SR-29 in Napa, then westbound SR-12, then southbound SR-121.

What's next

Caltrans has also scheduled closures from 10 p.m. Friday, Nov. 13, to 5 a.m. Sunday, Nov. 15, to shift traffic and barriers onto the eastbound side. All work depends on the weather.

Sources: Caltrans District 4; ABC10.