A cold front swept through the Bay Area on Monday to cover the highest peaks in the region with a light dusting of snow, while surprised drivers and delighted children dealt with a blanket of hail that clobbered commuters.

In Oakland, the hail was ample and resembled snow as children attempted to sled down white hills. Throughout the morning, there were reports of ice raining down across the region, said Ryan Walbrun, a meteorologist with the National Weather Service.

“It’s the type of a day where it’s not going to discriminate,” he said. “The air mass is so cold, really, anywhere showers fall there will be that hail threat.”

In the eastern parts of Contra Costa County, there were reports of heavy showers that resulted in “pea- to dime-sized” chunks of ice, according to the National Weather Service.

As the barrage of hail beat down on commuters, traffic jams were reported on Highway 13 near Piedmont, and Oakland police helped drivers navigate icy conditions. In Berkeley, people quickly ducked for cover, and elsewhere in the region lightning reportedly lit up the skies.

The surprising storm contributed to “a really cold upper-level trough” moving through the state, bringing snow to the highest peaks at 3,000-feet elevations, including Mount Diablo and Mount Hamilton, said Rick Canepa, a meteorologist with the National Weather Service.

“It’s tending to be a much more scattered type of precipitation coverage,” he said.

San Francisco received a quarter-inch from the time rain started falling Sunday evening into Monday morning. Oakland got .40 inches of rain. The biggest downfall reportedly hit Marin County, which got two-thirds of an inch, while San Mateo County and the North Bay, near St. Helena, each received .51 inches of rain.

“Elsewhere, it’s pretty much down to a third of an inch to .20 inches,” Canepa said. The light smattering was a welcome sign after a particularly dry water year. “It would be more ideal if it was a widespread rain, but this is not too bad.”

Since Oct. 1, when the water year started, San Francisco has received 17.15 inches of rain. The normal amount for the same period is 21.93 inches. Oakland has received 14.94 inches of rain in the same time period, while the precipitation standard is 19.08 inches. Santa Rosa had 24.2 inches of rain, whereas the normal amount is 33.35 inches, and San Jose had 8.88 inches of rain measured — almost 6 inches short of its standard 14.5 inches.

The rain and hail should subside the rest of the week to make way for a cold front followed by a warm weekend, according to forecasters.

“It’s going to be colder than normal for this time of year,” Canepa said.

San Francisco should see temperatures in the low 60s — 5 to 7 degrees lower than average for this time of year — and Oakland will be about 6 degrees below its normal temps this week, with most days registering highs in the upper 50s to low 60s. Temperatures in the North Bay will be in the mid-50s for the week, close to 10 degrees below normal.

San Jose should see the biggest change at roughly 15 degrees below average for this time of year, with temps in the upper 50s to low 60s.

By Friday, forecasters expect temperatures to climb back into the 70s, paving the way for a sunny Saturday and Sunday.

“The timing looks good for people who have the weekend off,” Canepa said.

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