Snow in August? California's Sierra Braces for Rare Summertime System

The ski season in the Sierra Nevada is still months away, but a weather whiplash is in the cards this weekend.

Forecasters expect a surprisingly strong low-pressure system originating from the Gulf of Alaska to dip into California from the Pacific Northwest on Friday, weakening the high pressure that usually dominates the atmosphere above the West Coast in August and keeping the region toasty.

Snowflakes could fall on the mountain’s highest peaks as temperatures drop to freezing, inaugurating the first snowfall of the 2024–25 season. Friday could be the coldest day of the week, but chilly temperatures might last through the weekend.

The National Weather Service cautions hikers, backpackers, and campers to consider the cold, windy weather if they head to the Sierra this weekend.

“It’s a pretty cold system for this time of year,” Sacramento-based weather service meteorologist Katrina Hand said. “We’re expecting up to a half-inch or an inch at the highest peaks.”

Hand said most of the rain and snow will likely fall north of Interstate 80 at elevations above 8,000 feet. But snow could drop from Mammoth to Yosemite to north of Tahoe. Summertime “snow has not occurred in these locations for at least 20 years,” according to the weather service office based in Hanford.

The northernmost parts of the Bay Area — Marin, Napa and Sonoma counties — could also receive about 0.1 inches of summertime rain.

“We describe it as climatological anomalous, which means we don’t expect these types of storm systems this time of year,” Hand said.

The Shasta area could see the most significant possible rainfall totals. Hand said lighter amounts could fall further south and into valley areas. Temperatures at lower elevations, around 5,000 feet, could reach as low as 50 degrees, akin to winter weather.

This past week, a different low-pressure system from the north brought mild and foggy weather around the Bay Area. This second system, set to arrive on Friday, will be deeper and pretty unusual for this time of year, according to the weather service.

Closer to the coast, they forecast an increased likelihood of cooler temperatures across the Bay Area beginning Friday and a 10% to 40% chance of up to 0.1 inch of rain in the North Bay.

“We’re not looking at a deep soaker or anything. It’s pretty much confined to through the day Friday, and if we get anything, it’s going to be pretty light,” said Dalton Behringer, a meteorologist with the weather service’s Bay Area office.

The North Bay typically receives a tiny amount of rain in August, normally about 0.04 inches (basically a drop or two).

“If this system were in the winter, it would definitely be a bigger rainmaker,” said Roger Goss, a weather service Bay Area office meteorologist. “We don’t expect the rain to be that big of a deal, but the cooldown will be more of a big deal.”

Sunshine and above-average temperatures are expected to return by early next week, when inland temperatures could reach triple digits. At the same time, the weather service forecasts that the San Francisco area will hit the mid-70s to low 80s.

“It’s going to warm right back up as we head into next week,” he said.