It is one of the closest things we have to a season.

And as the first day of summer breaks over San Diego and Riverside counties, the reliable late-spring weather phenomenon known as "June gloom" is showing signs of giving way to the drier, clearer pattern that dominates during the hotter months.

But up until the middle of last week, the region was covered from the coast to the inland valleys with a gloomy blanket of low clouds and fog.

The polar opposite of the hot, dry Santa Ana winds of autumn that spread desert-style heat throughout the region, the moist clouds of May and June spread coastallike coolness far and wide.

That annual "May gray" and "June gloom" pattern was late in arriving this spring, with May roaring in on the warm side, Bill Patzert, a climate scientist at NASA's Jet Propulsion Laboratory in Pasadena, said in a telephone interview last week. But the thick marine layer associated with the pattern was particularly pronounced this June -- so much so that temperatures were on the mild side just about everywhere in Southern California.

"I call it Southern California's natural air conditioner," Patzert said.

And condition the air it did.

Consider this: Through Wednesday, Palm Springs, which is usually baking in triple-digit temperatures every day this time of the year, had cracked the century mark only once this month. According to statistics kept by the National Weather Service, temperatures in the Riverside County desert resort city were running 7 degrees below normal.

Farther west, daytime highs in Temecula were running 10 degrees below normal.

According to Temeculaweather.com, residents there basked in 70-degree temperatures every day save for June 2. Normally at this time of the year, temperatures in the Wine Country community average in the middle 80s.

Similarly, Ramona temperatures were running about 4 degrees below normal through Wednesday, with just two highs in the 80s, National Weather Service records show.

And temperatures were running about 1 degree below normal along the San Diego County coast.

Through the middle of last week, Carlsbad had warmed into the 70s on just three occasions in June.

Love it or hate it

That's hardly swimming weather, said Kelly Vrooman, a bank teller from Temecula who isn't particularly fond of June gloom and would just as soon see the clouds make an early exit.

"It just makes you feel lazy and not have as much energy," Vrooman said.

It hasn't helped that her daughters' birthdays are June 13 and 17, respectively. Her girls are 23 and 24 now. But when they were growing up, they always wanted pool parties in the back yard.

And it was always overcast.

"My kids had more birthday parties in June gloom, and it was just horrible. I felt so bad for them," Vrooman said. "You got out of the pool and you were freezing."

While many share Vrooman's dislike for the overcast days of June, others like them.

"It gives you a chance to wear sweaters and clothes you wouldn't normally wear in this area," said Steve Aceti, who lives in Encinitas and serves as executive director for the California Coastal Coalition, a group that lobbies for legislation friendly to coastal communities.

"And you know that it's going to clear up, and you are going to have much better weather in late summer and fall," Aceti said.

Pat Yeakley of Leucadia also likes the clouds.

"Frankly, if I could choose between frying and June gloom, I'd pick June gloom," Yeakley said. "We live half a mile from the ocean, and we don't have air conditioning."

She said that on one particularly hot day in May, the temperature in her house soared to 87 degrees.

Up on the Santa Rosa Plateau, Rob Hicks, a park interpreter for the Riverside County Park District, also is a big fan of the clouds. He said the extended coolness has lured more visitors to the scenic oak-covered reserve near Murrieta.

"I'll take these 70-degree temperatures any day," Hicks said. "I know that anyday now, the oven's going to get turned on. I know that we will have three or four straight months of the exact opposite."

For those who moved here recently or reflect on the region's reputation as a sunny paradise, the idea that thick clouds could dominate the weather for weeks on end may appear to be the opposite of what should be normal or natural.

June gloom's engine

But scientists say June gloom is a natural occurrence, and all of the region's features play a role in its formation.

For starters, said Patzert, of the Jet Propulsion Laboratory, high-pressure systems tend to form over the eastern Pacific Ocean during May and June, driving northwesterly winds down the West Coast. South of Point Conception, the winds turn toward the coast and spin counterclockwise around Santa Catalina Island, giving birth to something that weather people like to call the Catalina eddy.

At the same time, the ocean is still cool, coming out of the winter. But the land is warming dramatically in the nearby deserts. And because hot air tends to rise, the air mass over inland areas rises and creates a vacuum.

"Then the air from the ocean tries to replace it," said Stan Wasowski, a forecaster with the National Weather Service in Rancho Bernardo.

As a result, the marine layer is sucked far inland, all the way to the mountains, Wasowski said.

Those mountains play an important role, too, he said. They prevent the blast-furnace desert air from rolling back to the coast.

If not for the rugged peaks of Mount Laguna, Palomar Mountain, Mount San Jacinto and the San Bernardino Mountains, he said, "We would be in big trouble. You would probably see a climate like Morocco, where there is heat all the way to the coast because there would be no mountains to block it."

The way Wasowski sees it, there are plenty of reasons to celebrate this year's heavy June gloom.

"We haven't had to water as much. We haven't had to cool our houses at all," he said. "I don't know how anybody can complain about weather like this."

Indeed, Patzert said, "When we get into July, August and September, we're going to remember these past three weeks fondly."

Call staff writer Dave Downey at 760-745-6611, ext. 2623.