Thunderstorms could bring flash floods to Northern California. When to expect rain
Thunderstorms could roll across Northern California this week.
According to the National Weather Service, these thunderstorms could bring rain to Northern California and parts of the Central Valley — including Sacramento, Modesto, Merced and Fresno.
“Heavy rain is likely with any storms that develop, leading to flash flooding concerns especially in Shasta County,” the weather agency said Monday, Aug. 25, on X.
There’s a 20% to 40% chance of storms, the weather service said, with the highest chances occurring across the Coast Range, Shasta County, Sierra Nevada and southern Cascades, the post said.
Some areas of the Valley will also see light rain, the weather service said.
Am I at risk for flash floods?
According to the National Weather Service, flash floods can happen for several reasons, but they’re most often caused by very heavy rain from thunderstorms.
Flash floods can happen “so quickly that people are caught off-guard,” the weather agency said.
Just how quickly can depend on where the rain falls and how hard, as well as the shape of the land, the type of soil, how wet the ground already is and even how much vegetation is around, the weather service explained.
According to the National Weather Service, there is a higher risk for flash floods in Northern California — especially in Shasta County.
“Their situation may become dangerous if they encounter high, fast-moving water while traveling,” the weather agency said. “If people are at their homes or businesses, the water may rise quickly and trap them, or cause damage to the property without them having a chance to protect the property.”
Are thunderstorms common this time of year?
Courtney Carpenter, a meteorologist with the National Weather Service, previously told The Sacramento Bee that thunderstorms aren’t frequent this time of year.
“They’re not super frequent, but we can get them when monsoon moisture comes up north from the desert,” Carpenter told The Bee in August 2024.
What should I do if I’m caught in a thunderstorm?
When you are caught in a thunderstorm, follow these tips from the National Weather Service if a safe location is not nearby:
- Avoid beach picnic shelters
- Avoid the tops of hills and open fields
- Avoid water
- Avoid trees and other tall objects
“Remember: if you see a flash, dash inside,” the agency said on X.
Will it rain in Sacramento?
In areas across Northern California, the National Weather Service said, there will “showers and thunderstorms.”
According to the weather agency’s latest forecast for Sacramento, there will be “a slight chance of showers” between 3 and 4 p.m. Tuesday, Aug. 26, with light winds at around 6 to 9 mph.
Where else will it rain?
In Modesto, Merced and Fresno, there’s a 10% chance of showers on Monday evening, rising to 30% on Tuesday.
This story was originally published August 25, 2025 at 12:58 PM with the headline "Thunderstorms could bring flash floods to Northern California. When to expect rain."
