Highway 37 to be closed this weekend for El Niño prep work. Here's what to know.

Drivers who rely on Highway 37 in the North Bay should expect delays, as Caltrans is closing a stretch of the roadway the entire weekend to make El Niño-related winter storm preparations.

Officials said the roadway between Mare Island in Vallejo and Sears Point in Sonoma County will be closed for 55 hours, from 10 p.m. on Friday, Oct. 23 through 5 a.m. on Monday, Oct. 26.

To prepare for the weekend closure, all westbound lanes between Mare Island and Sears Point will also be closed from 7 p.m. Thursday through 4 a.m. Friday.

During the closure, workers will demolish the median and install K-rail to shift both directions of traffic to the westbound lanes. Crews will then raise portions of the eastbound lanes by three feet to address flooding concerns.

With very few alternate routes, Caltrans is recommending two lengthy detours around the closure.

For westbound 37, drivers should take the Highway 29 / Sonoma Boulevard in Vallejo and turn right, heading towards Napa. Drivers will then follow Highway 29 to westbound Highway 12 (Carneros Highway) and then to southbound Highway 121 to Highway 37 at Sears Point.

Drivers using eastbound 37 will take northbound 121, make a right on the Carneros Highway (Highways 12 and 121), followed by a right on Highways 12/29, rejoining Highway 37 in Vallejo.

"The detours that are going to be in place for this 40-mile detour, over an hour, that's just the reality of the North Bay," Caltrans spokesperson Bart Ney told CBS News Bay Area on Oct. 15.  "There isn't the redundancy of routes that you see in other places in the Bay Area, or California for that matter. So, whenever we lose 37, we see how important that route actually is."

Caltrans is also planning supplemental closures of Highway 37 starting Friday, Nov. 13 at 10 p.m. to 5 p.m. on Sunday, Nov. 15. All work will be dependent on weather conditions, officials said.