San Diego is likely to have unusually cool weather on the 4th of July

The National Weather Service says San Diego is likely to be unseasonably cool on July 4, with a daytime high only reaching 69 — five degrees below average.

A low pressure system that is currently about 500 miles off the West Coast will move inshore late Sunday, sending a lot of cool, moist air ashore on Monday.

Wind-driven moisture could produce upwelling, which brings deeper, cooler water to the surface. This phenomenon can limit warming along the coast.

“The mean highs don’t change much in the summer,” said Joe Cordero, an analyst with the weather service. “But we could have a swing and this could be one of the coolest Fourth of Julys we’ve had in years.”

A reading of 69 would represent the coolest Fourth of July in San Diego since 2012, when the temperature was just 67.

This depression will produce more coastal clouds. But Cordero says it doesn’t look like a thick sea layer will form before fireworks shows erupt across the county.

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