The National Weather Service says a weak low pressure system could produce dangerous lightning and loud thunder on Tuesday night as it moves through San Diego County.
The unstable air will likely drop into the county from the north around 6 p.m. and spread south, possibly reaching coastal areas, where lightning is a rare occurrence. Thunder and lightning could last well into the evening and be accompanied by short spurts of rain.
Forecasters say people should immediately seek cover if they hear thunder or see flashes of lightning. The temperature of lightning bolts can reach about 50,000 degrees — five times hotter than the surface of the sun.
Lightning will be a particular concern in the eastern half of the county, where many areas have gotten only about half of their usual seasonal rainfall. Much of that region is covered by chaparral and grassland, which can be very flammable.
