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SAN DIEGO — Lightning and thunder marked the arrival of the first of two winter storms that will bring plenty of rain and snow to San Diego this weekend.

Residents reported loud claps of thunder as they got ready for bed late Thursday, and the National Weather Service confirmed at least 75 “cloud-to-ground” lightning strikes in Southern California overnight. The service recorded about 30 more flashes in the clouds.

Drivers woke up to rainy conditions on local freeways early Friday and officials urged San Diegans to use caution on their morning commute. A big rig jackknifed on Interstate 15 in the rain, leading to a deadly crash.

The cold, wet weather makes a significant departure from a week that started with warm and sunny conditions.

“We are in for quite the change from the summer-like weather we have seen this week,” the NWS said on Twitter. “Two large storm systems will produce heavy rain, mountain snow and strong winds.”

The rain that started late Thursday and lasted through the night was expected to be the heaviest of the two systems, forecasters said. By about 4:30 a.m., NWS predicted the most intense thunderstorms had already passed. Showers were still expected on and off throughout the day Friday.

A second, lighter storm will then bring more scattered showers ranging from Friday night into Sunday morning.

High temperatures also dropped significantly, turning “sharply colder Friday through Sunday,” according to NWS. High temperatures were as much as 20 degrees below average for the mountains and inland valleys, and it was only expected to reach the high 50s and low 60s on the coast. Saturday will be another few degrees cooler, forecasters said.

Officials issued a winter weather advisory for San Diego County mountains that lasts from late Friday night until 2 a.m. Sunday. The advisory is in effect for areas above 4,500 feet, where the heaviest rain was expected to fall and 2 to 4 inches of snow could accumulate.

San Diego’s desert communities were under a wind advisory from 7 p.m. Thursday to noon on Saturday, NWS said. Wind gusts of up to 70 miles per hour are possible in some areas.

Throughout the storm, you can track conditions with FOX 5’s San Diego weather radar and live San Diego traffic map.