‘Dangerous’ four-day heat wave to take hold across San Diego County on Friday

Beach temperatures will be in the 78 to 85 degree range during the heat wave
(Gary Robbins / The San Diego Union-Tribune )

Forecasters says there will be hot temperatures during the day and little cooling at night


The National Weather Service says a “dangerous” four-day heat wave will descend on San Diego County on Friday, producing temperatures in the 78-85 degree range at local beaches, the low-to-mid 90s in areas like Mira Mesa and San Marcos, and the low 100s in such inland communities as Ramona and El Cajon.

The temperatures will be in the 115- to 120-degree range in local deserts.

An excessive heat warning will be in effect from noon Friday until 9 p.m. on Monday, and forecasters say it is possible that the heat wave will extend into the middle of next week. The warning area will extend from roughly Interstate 15 east to the valleys and foothills below 5,000 feet, and into the eastern deserts.

The weather service says the heat wave poses a potentially dangerous threat because it will produced sustained heat during the day and unusually warm conditions at night. The system poses a particular threat to people with weak respiratory systems.

The heat wave will drive people to the coast, where sea surface temperatures have been cooler than normal due to coastal upwelling. The water was in the 68- to 69-degree range on Wednesday afternoon along the San Diego County coastline. It is usually in the low-to-mid 70s this time of year.

San Diego International Airport also has been cooler than normal since the beginning of the month due to the affects of low pressure systems.

Tropical Storm Elida, which is still swirling west of the Baja California peninsula, will send warm moisture into Southern California. But forecasters say the system will not produce unusually humid conditions in San Diego County during the heat wave. And it is unlikely that the seasonal monsoon will dig in until sometime next week, at the earliest.