Northern California summer interrupted by thunderstorms
An unusual scene developed in the skies over parts of Northern California on Tuesday. Small thunderstorms have popped up in the region through the late morning hours.
Quite an unusual scene in the southern Sacramento Valley this morning. A few small thunderstorms going up!
— Nic Merianos (@NickMerianos) August 26, 2025
If you can hear thunder, you’re close enough to be struck by lightning.
Widespread storms this afternoon for the Sierra with Flood Watches posted for the eastern slope,… pic.twitter.com/BorRxmlGsp
The activity was focused north of Sacramento through early morning, but the storms then began moving southward. Thunderstorms, brief heavy rain, lightning and hail all occurred with this system.
Even areas further south, like southeast of Modesto and eastern Stanislaus County, are seeing active weather on Tuesday.
Isolated showers and thunderstorms are already developing in the valley, with more action expected in the mountains this afternoon. ⛈️
— Ashley Nanfria (@ashleynanfria) August 26, 2025
Keeping an eye on a few thunderstorms north of Sacramento and southeast of Modesto. #cawx pic.twitter.com/FhZ5iw57AC
Come the afternoon hours on Tuesday, widespread storms are expected in the Sierra Nevada – prompting a Flash Flood Warning for the eastern slope, including for Truckee and the Lake Tahoe area along the I-80 corridor. The National Weather Service said the warning was in place until at least 6 p.m.
Ahead of the storms, the California Governor's Office of Emergency Services (Cal OES) predeployed additional fire engines and water tenders to Placer and Calaveras counties. Crews in Auburn and surrounding areas remain on standby should new fires break out.
"All it takes is six good lightning strikes to hit and you get yourself an ignition," said Rodney Hart, a Cal Fire research intelligence specialist.
Officials say this particular weather pattern is unusual for the region, with monsoonal moisture fueling the system.
Monsoonal moisture continues to fuel Sierra storms, as seen on this satellite timelapse. ⛈️
— Ashley Nanfria (@ashleynanfria) August 26, 2025
Be prepared for more thunderstorms this afternoon. #CAwx https://t.co/EGN7QvqRNW
"We're dealing with a situation that's kind of unusual for the Foothills of the Sierra Nevadas," Hart explained. "We have some lightning forming up in the morning and providing us with a few strikes."
Temperatures are still expected to be in the 80s to low 90s for most of Northern California on Tuesday.
As of around 3:30 p.m. Tuesday, there have been more than 8,500 cloud-to-ground lightning strikes over the previous 24 hours.
More than 8,500 cloud-to-ground lightning strikes over the last 24 hours! Very impressive pic.twitter.com/3CfNGmldnw
— Nic Merianos (@NickMerianos) August 26, 2025
Even after storms move out, the danger isn't over. Cal Fire says lightning strikes can smolder for hours before flaring into flames once humidity drops and winds pick up.
Cal Fire says crews will continue monitoring conditions as storms move through the region.
"It just smolders and smolders," Hart said. "Once those clouds go away and the humidity levels dry, a little bit of wind can spark it and the next thing you know we could have a fire that's significant."