The monsoon might spark lightning along San Diego County coastline this weekend

The flash and crackle of lightning are rare along the San Diego County coastline. But there’s a 15 to 25 percent chance that it will happen this weekend as the monsoon pushes moist, unstable air west of the mountains, says the National Weather Service.

“We’re expecting some prizes between Friday night and Monday morning,” said Alex Tardy, a weather service forecaster. “Lightning could appear in San Diego, or farther up the coast, or in places like El Cajon and Escondido.”

Although the chances of lightning aren’t super high, forecasters always cite such figures because thunderstorms pose a public safety hazard. And there are a lot of large outdoor events this weekend, including a three-game home stand at Petco Park, where the Padres will host the Minnesota Twins.

There also will be horse racing at Del Mar and the opening of the Ramona Country Fair.

Forecasters say people who plan to be in wide open places, such as a golf course, should go inside immediately if they hear thunder.

The weather service says the chance of lightning on Saturday and Sunday is 20 to 30 percent in the valleys, 35 to 45 percent in the mountains, and 25 to 35 percent in the deserts.

Thunderstorms increase the risk of wildfire, especially in East County, where the chaparral is drier than it has been in years.

Since the rainy season began on Oct. 1, San Diego International Airport has received 6.08 inches of precipitation, which is 64 percent of normal. Ramona Airport has recorded 9.47 inches, which is 67 percent of normal.

Temperatures will be in low 90s Friday through Sunday in El Cajon and the low 100s at Borrego Springs.

San Diego will be 73 on Friday, 75 on Saturday and 76 on Sunday. A patchy marine layer has kept the coast cooler than average throughout most of July.