An upper-level high pressure system will continue to allow moist, tropical air to flow north, creating uncomfortably muggy conditions today, the weather service predicted.
The system, however, should begin to shift Sunday, and temperatures will cool off Sunday and Labor Day, said Ray Robben, a National Weather Service forecaster.
Coastal areas today should have patchy, early-morning low clouds that will burn off to mostly sunny skies and hot temperatures.
Daytime temperatures will be in the 85- to 90-degree range today and about 5 degrees cooler Sunday and Monday, Robben said. Nighttime lows will be about 70.
Temperatures in the inland areas will continue to soar into the 100s through Labor Day. High humidity levels will make conditions especially uncomfortable in the foothills, Robben said, where the heat will feel 10 to 15 degrees warmer than it actually is.
The overnight temperature should drop to 69.
Friday's temperature at Lindbergh Field was a warm 90, only 3 degrees shy of the record set for the same date in 1909.
Although no smog alert was declared in San Diego County Friday, the air quality was poor in many inland areas, and those conditions are expected to continue today.