It wasn’t a drenching atmospheric river. But the biggest storm to hit the Bay Area in roughly 7 months began to douse much of California on Monday afternoon, slowing motorists, dropping snow in the Sierra Nevada, and providing a clear signal that the winter rainy season has begun.

Come Tuesday the atmosphere will begin shedding the Monday blues, and the rest of the week should be about as good as October gets. Highs should be in the low and mid-60s, a few shades below normal, with wall-to-wall sun through Sunday, forecasters say.

The rainy season has officially started in the Bay Area as a storm is expected to bring nearly a month’s worth of rain to San Francisco in less than 24 hours, according to the National Weather Service.

Archuleta County Sheriff Mike Le Roux said “continuous rain” started early Monday in and near Pagosa Springs, and the water levels were slowly rising.

A storm like this is rare for October, forecasters said.

An incoming storm, powered by the lingering bits of Tropical Storm Priscilla in the Pacific Ocean, could bring heavy rain and flooding to parts of Southern California to start the week.

There can be downpours at times, so just be mindful of water on the roadways,” said NWS meteorologist Roger Gass.

Heavy rains from the remnants of Tropical Storm Priscilla caused significant flooding across parts of Arizona on Sunday. Here's what to expect.

Swiftly moving rain showers are on their way to the Bay Area, bringing chances of thunderstorms, gusty winds and localized flooding in their wake.