For the second time in two weeks, an unusual heat wave is building over San Diego County.
Temperatures across the county could reach 20 degrees above average on Thursday and Friday — from 90 degrees in the inland valleys to the upper 80s along the coast.
Mild Santa Ana winds combined with a high-pressure system are again pushing the cool marine layer out to sea and allowing the atmosphere to heat up.
“With the dry air, with the warm air and the warm sea surface temperatures, it has an impact on the marine layer, making it less effective,” said Alex Tardy, meteorologist with the National Weather Service. “It makes it smaller, not as deep, it burns off quicker.”
The heat wave is expected to break down starting Saturday, but overall the persistent hot and dry pattern is predicted to continue.
“Because of the severe drought, now four years running, because of the warm sea surface temperatures and because of the weather pattern,” Tardy explained, “we do expect a warm spring carrying right into the summer.”
Tardy said this week’s heat puts the exclamation mark on what has already been the warmest March on record. Daytime high temperatures have averaged approximately 5 degrees above the normal 66 degrees, according to data from the National Weather Service.
“We can’t buy a break it seems,” Tardy said. “Really, since 2014 we’ve been looking at record warm temperatures.”
A heat wave that gripped San Diego two weeks ago during the last weekend of winter shattered previous daytime high temperatures by as much as 9 degrees at Lindbergh Field.