Heavy rainfall Saturday night prompted Highway 101 closures in Montecito and a flash flood warning from the National Weather Service.
The northbound freeway was closed between San Ysidro and Olive Mill roads as of 10:30 p.m.
Southbound traffic reportedly was stopped because of roadway flooding, but at least one lane was reopened late Saturday, according to the California Highway Patrol.
The flash flood warning came after the Santa Barbara and Montecito area received more than a half-inch of rainfall in 15 minutes as heavy thunderstorms moved through the region, the weather service said.
“Tonight’s storm is causing major impacts across the South Coast,” Montecito Fire Protection District officials said in a social media message at 9:20 p.m.
“Please be aware of flooding, rocks, mud & debris in many local roadways.”
Montecito was being assisted by the Carpinteria-Summerland, Santa Barbara and Santa Barbara County fire departments due to the high volume of storm-related calls.
Hail covers Highway 101 on Ortega Hill in Summerland during Saturday night’s storm. Credit: Perry Simpson photo 
A vehicle plows through flood waters on North Jameson Lane in Montecito on Saturday night. Credit: Peter Hartmann / Noozhawk photo 
A large tree toppled across the 400 block of East Anapamu Street in Santa Barbara on Saturday night, damaging several vehicles. Credit: Peter Hartmann / Noozhawk photo 
Traffic on Highway 101 was stopped in Montecito for more than an hour Saturday night as a major storm moved through the area. This photo is taken from the southbound lanes at Olive Mill Road around 9 p.m. Credit: Stephanie Caldwell photo 
Flooding shut down Highway 101 through Montecito on Saturday night, creating a massive traffic backup. Credit: Ray Navarro / Noozhawk photo 
Flooding from Saturday night’s heavy rainfall shut down Highway 101 in Montecito, causing major traffic tie-ups. This photo is looking north from the San Ysidro Road overpass. Credit: Peter Hartmann / Noozhawk photo 
Hail blankets the Sheffield Drive underpass at Highway 101 in Montecito on Saturday night. Credit: Montecito Fire Protection District photo 
Carpinteria-Summerland Fire Department Engine 61 is parked at the Sheffield Drive underpass on Highway 101 late Saturday while crews were assisting stranded motorists. A tractor-trailer reportedly jackknifed after the driver attempted to avoid a downed power pole and blocked Ortega Hill Road, between Ortega Ridge Road and Sheffield Drive. Credit: Montecito Fire Protection District photo 
Southbound traffic is blocked by freeway flooding on Highway 101 in Montecito on Saturday night, in a view looking south from the San Ysidro Road overpass. 
An elevated Montecito Creek flows toward the Hot Springs Road bridge during an afternoon break between Saturday’s storms. Credit: Peter Hartmann / Noozhawk photo 
Montecito Creek flows into the debris basin along Olive Mill Road on Saturday afternoon. Credit: Peter Hartmann / Noozhawk photo 
Montecito Creek rushing toward the debris basin along Olive Mill Road on Saturday afternoon. The Casa Dorinda bridge is in the background. Credit: Peter Hartmann / Noozhawk photo
The Montecito area had received more than 4 inches from the storm that started Friday, and more than 2 inches in a three-hour period as of 8:55 p.m., according to county Public Works rainfall monitoring stations.
The CHP reported flooded Highway 101 lanes and vehicles stuck in floodwaters throughout Montecito and Santa Barbara as of 8:30 p.m.
“The south side of the freeway is at a standstill and people are getting out of their cars to walk around,” said Stephanie Caldwell, president and CEO of the Ventura Chamber of Commerce, who was stuck in the flooding-related traffic jam near Olive Mill Road for more than an hour on Saturday night.
“They cleared all the cars on the other side by making them back up and exit,” she told Noozhawk around 9:30 p.m. “My side is still not moving.”
When a freeway path was finally cleared, she described passing stranded cars with “water up to their doors.”
“Turn around, don’t drown when encountering flooded roads,” the weather service said. “Most flood deaths occur in vehicles.”
The Santa Barbara County Office of Emergency Management sent out alerts at 8:32 p.m. Saturday warning residents in Goleta, Santa Barbara, Montecito and Summerland to avoid areas near creeks or streams, low-lying areas and recent wildfire burn areas.
“A flash flood is an extremely dangerous, sudden, violent and fast-moving wall of water,” OEM said in its message. “Avoid recent burn areas, low-lying areas, areas with standing water, and areas near creeks or streams.
“If you are in one of these areas, go to the innermost room of your home or to higher ground, such as a second floor.”
Localized flooding was reported in numerous areas around Montecito and Santa Barbara, with some residents reporting water coming into their homes.
Multiple downed trees and power lines also were reported in Saturday night’s storm.
Check back with Noozhawk for updates to this story.