First rain of wet season dumps 2 inches of rain in some parts of Bay Area

A storm system on Tuesday brings some much needed precipitation to the region. (File Photo) A storm system on Tuesday brings some much needed precipitation to the region. (File Photo) Photo: Carlos Avila Gonzalez / The Chronicle Buy photo Photo: Carlos Avila Gonzalez / The Chronicle Image 1 of / 22 Caption Close First rain of wet season dumps 2 inches of rain in some parts of Bay Area 1 / 22 Back to Gallery

The first storm of the wet season Tuesday dumped roughly an inch of rain on parts of the Bay Area, making roads especially slick for early morning commuters.

The bulk of the storm occurred in the North Bay. Places such as Petaluma, Santa Rosa and Sebastopol were doused with more than an inch of rain, according to the National Weather Service.

Regions of Sonoma County saw heavier rainfall, such as the unincorporated mountain community of Venado, where officials recorded more than 2 inches by 11 a.m.

The downpour also had an unexpected impact in San Rafael, where part of a HomeGoods store’s roof collapsed. San Rafael recorded roughly 1.39 inches just before noon.

Firefighters responded to an alarm activation early Wednesday and discovered the partial collapse near the entrance of the store, according to the San Rafael Fire Department.

Luckily, the store was closed and no injuries were reported.

Meanwhile, San Francisco had received close to a tenth of inch by about 7 a.m., but the main “precipitation band” of the storm hadn’t yet swept into the city, said Drew Peterson, a meteorologist with the National Weather Service.

By noon, San Francisco recorded roughly a quarter of an inch, according to the National Weather Service.

This is the first measurable rainfall in San Francisco since June 9, when .01 inches were reported.

The East Bay and South Bay haven’t been affected much by the latest storm, garnering about a tenth of an inch or less of rain throughout the two regions.

Top 24 hr rainfall total in the region comes from the tiny community of Venado in the mountains of Sonoma county with 2.20" However Phoenix just edges them out with 2.24" #cawx #azwx — NWS Bay Area (@NWSBayArea) October 3, 2018

Tuesday’s rainfall should linger through Wednesday, Peterson said, but the showers are “going to be really spotty.”

“Most locations will pick up at most an additional few hundredths, if any at all,” he said. “Most areas won’t get hit by these showers.”

Temperatures throughout the Bay Area will stay mild before a warming trend this weekend.

On Tuesday, San Francisco is expected to reach 68 degrees, Oakland will hit 73 degrees and San Jose will climb to 78 degrees.

Similar temperatures will continue throughout the week, give or take a few degrees, Peterson said.

By Friday night, overnight temperatures in San Francisco, Oakland and San Jose will drop to the mid 50s.

Temperatures for Petaluma and Santa Rosa will remain in the 70s for most of the week before reaching the 80s on Saturday and Sunday.

Because the storm is the first of the season, forecasters warned, motor oil built up on the roadways can make driving more dangerous due to slick patches. Morning commuters should slow down and use headlights whenever their wipers are on, Peterson said.

“This is the very start of the wet season,” he said. “So, it’s not usual to see these run-of-the-mill weaker systems when we first start to get our rainfall.”

San Francisco Chronicle staff writer Lauren Hernandez contributed to this story.

Sarah Ravani is a San Francisco Chronicle staff writer. Email: sravani@sfchronicle.com Twitter: @SarRavani