From Storms to Sunscreen: Bay Area Weather Turnaround Is Here

After a weekend of downpours across the Bay Area and snow storms in the Sierra Nevada, forecasters expect a complete weather turnaround this week.

“Sunscreen is going to be important,” said Dalton Behringer, a meteorologist with the National Weather Service’s Bay Area office. “We’ve had some clear days, but this is going to be the warmest period this year.”

Temperatures over the next week could reach 90 degrees in some areas of the Central Valley, into the upper 80s in inland parts of the Bay Area, and the 70s in the Sierra Nevada.

The warm weather comes just days after storms dropped up to two feet of snow across the Sierra, blanketing the mountain range in fresh powder — and delivering the heaviest single-day snowfall of the 2023–24 season, according to the UC Berkeley Central Sierra Snow Lab.

Although such weather shifts aren’t irregular for the shoulder season transitioning into summer, this week’s turnaround may be drastic in some areas. The warming bears fingerprints of climate-change-driven swings between extreme precipitation and drying out, climate experts said, but it isn’t abnormal for May.

“This isn’t necessarily in the realm of extremes,” Behringer said. “Whenever we talk about weather whiplash, we usually talk about more extreme levels than this.”

Still, the temperatures prompted NWS advisories for people sensitive to heat and the unhoused population, especially those in the South or East Bay.

Scott Rowe, senior service hydrologist with NWS in Sacramento, said that because night-time temperatures will drop, forecasters don’t expect the warm-up to cause too much melting of the snowpack, which statewide is at 99% of the average for this time of year.

“I wouldn’t classify this as a heat wave,” he said. “Overnight temperatures are going to stay cool, and that’s going to provide ample relief.”

Still, Rowe expects an increase in runoff over the next week. This is vital to water managers because the snowpack fills reservoirs as it melts in the spring and summer, providing water that millions of Californians and farms rely on. However, melting that occurs too rapidly can cause problems with flooding and an early depletion of the snowpack.

The snowmelt over the next week could be kept in check by the new layer of bright white that fell on top of older, dirty snow, which can slow melting, said Andrew Schwartz, lead scientist at the UC Berkeley Central Sierra Snow Lab.

While this past weekend’s storm represents the single snowiest day in May in recorded history in some parts of the Sierra, it’s not enough to totally prevent melting overall as temperatures heat up. Schwartz said if the warm temperatures last for weeks, major melting could occur, threatening the life of the snowpack.

“That could create a lot of snowmelt … but it’s not necessarily anything that’s throwing up red flags for us right now,” he said.

The warmer conditions are expected to last more than a week before a slight chance of wetter weather as storm season gives way to a “summertime pattern,” according to Behringer, the NWS meteorologist.

As the cool days turn into hot days, Schwartz noted that an abnormal snowfall followed by a drying pattern is a “signature” of a warming world marked by human-caused climate change.

“Increased severity of events is definitely a fingerprint of climate change, but it’s not the whole story,” he said. “In these shoulder seasons, we occasionally have large snowfall events, and that’s happened for a long time. So, it’s kind of both natural variability and the climate change component.”