SAN DIEGO — In Southern California, summer opened with a rare and welcome treat: the sun.

Coastal cities like San Diego and Los Angeles have been mired in thick and seemingly endless fog for weeks. The cloud cover, known to locals as “May Gray” and “June Gloom,” is common in late spring and early summer, but this year seems different, and meteorologists are fielding questions about how long the gloom will last.

While much of the continent is roasting under heat domes — in Canada, Mexico and Texas — coastal Californians have been shivering for most of the year, including this spring.

Skies cleared briefly this week, and San Diego hit 73 degrees on Tuesday and Wednesday, the warmest days since April 22.

“This is a temporary reprieve,” said Joe Sirard, a meteorologist with the Los Angeles National Weather Service. “Unfortunately, clouds are going to make a big comeback … but I don’t think we’re going to be socked in for days on end like we were recently.”

Rare glimpses of sun

Although coastal clouds are typical this time of year, it’s not normal for sunshine to be quite so fleeting.

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In San Diego, there were no clear days in all of May and for the first half of June, according to Alex Tardy, a meteorologist at the National Weather Service office in the city. On average, about eight days in May and nine in June would see clear skies from sunrise to sunset. Instead, the city saw 20 cloudy days in May, which is double the norm, and June already had seen 13 through Tuesday. The marine stratus has often extended well inland and to higher elevations, enshrouding mountain roads and communities.

“When we do get sunshine, it has been a really nice break, especially when we get it in the afternoon hours when the sun is high,” Tardy said in an online briefing Friday.

Brandt Maxwell, another meteorologist at the San Diego office, combed through historical records at four area weather stations and found that solar radiation ranked lowest in May 2023 at each location.

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Sunshine was also elusive this past winter because of repeated storm systems. But even in between the storms, skies were cloudier than normal.

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“That was really noticeable — in between all the rain events, we had a lot of partly cloudy days,” Tardy said. “But what’s been really noticeable in May and June is the cloudy days — the days with about 80 percent or more cloud cover.”

Temperatures in San Diego have also been running below normal every month since November.

What’s behind the cold and fog?

The thick marine layer is mostly due to very cold water along the coast, which chills and condenses moisture in the air above it. This spring, coastal waters were particularly cold, a result of the active storm track this winter, Tardy said. The prevailing winds allowed colder waters to upwell from deeper in the ocean.

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In April, Scripps Pier in La Jolla, in northern San Diego, recorded a water temperature of 52 degrees, just shy of the all-time coldest reading of 50 degrees. This is a stark departure from ocean temperatures in most of the world, which are setting records for warmth.

Looks like our natural A/C just got a tune-up, or should we say... turned down? Based on the Scripps nearshore sea surface temperature anyway, we are tracking well below the daily mean for mid June. #CAwx pic.twitter.com/eGh9ICCc43

— NWS San Diego (@NWSSanDiego) June 20, 2023

Moreover, the jet stream has largely been aimed at California since May rather than hovering over Canada, where it should be this time of year. Weather systems off the Pacific have helped to lift and cool the marine layer, extending it up to 5,000 feet in altitude — thick enough to form drizzle. Troughs of low pressure continue to drop into the state, bringing windy and cool conditions — a pattern more characteristic of March than June.

Well, we tried 🤷 We hope everyone enjoyed a taste of summer yesterday (the amount traffic sure seemed like it 🙄🚗) !

Another troughing pattern will be bring more cooler & breezier weather for inland areas, with more **typical** June gloom closer to the coast this week. #CAwx pic.twitter.com/1EbgvZ6vVb

— NWS San Diego (@NWSSanDiego) June 18, 2023

Will it warm up this summer?

The cool and cloudy weather is expected to continue in June, but there are signs that a shift is on the horizon. Summer heat could arrive in July, while longer-range outlooks favor above-normal temperatures for the West Coast — and for much of the nation — through September. That may be a mixed blessing, as several wildfires have sparked in Southern California during the briefly warmer and breezy conditions this week.

Given the intensity of recent summer heat waves, Californians may be wishing for a return of the marine layer in the coming months.

“It certainly helps with the air conditioning bill, that’s for sure,” said Sirard, the Los Angeles meteorologist.

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