For the second straight day, temperatures dropped were 10 to 15 degrees below average in parts of San Diego County before dawn Tuesday, and the air could be nearly as cool on Wednesday, the National Weather Service said.
The overnight temperature at San Diego International Airport fell to 49 early Tuesday. The seasonal average is 59. Miramar slipped to 44, which is about 11 degrees below normal. And Oceanside Airport, which is located inland, fell to 37. The weather service said the pre-dawn temperature at that airport averages 52 this time of year.
“This happened because we had really clear skies, very low relative humidity and light or no winds in many places,” said Joe Dandrea, a weather service forecaster.
The conditions were mostly caused by Santa Ana winds, which tapered off on Monday, allowing cool air to descend to the surface.
