Astronomers will tell you that summer arrives with the solstice on June 21, at 6:09 p.m.
But Maryland highway officials, innkeepers and the thousands of families with a pent-up urge to soak up sun at the beach or head for the mountains know otherwise: Summer begins today, with the start of the Memorial Day holiday weekend.
And at Ocean City, where the economy follows the weather, tourism officials will be starting the season with a good omen -- a near-ideal forecast of mostly sunny days and fair nights.
"I think we'll have a big Memorial Day," says Ocean City Mayor Roland E. "Fish" Powell. "The key to all of it is the weather. If you have stinking weather at a beach resort, it doesn't matter what the economy does."
The resort's public relations office predicted a weekend crowd of 250,000 to 275,000 visitors -- numbers comparable to the "Demoflush" population figures of 259,212 last year, and 272,752 in 1991.
(The estimates are flushed out with a formula based on Ocean City's wastewater flow.)
Temperatures are expected to reach the upper 80s today -- perhaps even 90 in asphalt-laden Baltimore City -- to boost that summertime feeling.
"The only fly in the ointment," said National Weather Service forecaster Amet Figueroa, "is a weak cold front that will be moving through the area late Friday night and early Saturday. We could get a few showers, even a thunderstorm or two is possible in the state.
"But it's coming in at a very good time, overnight. The models indicate the front is going to go well south of the area during Saturday. With fingers crossed, we expect that Memorial Day weekend will be one we consider unusually pleasant."
Call it sunny, with temperatures reaching the upper 70s to near 80 degrees -- but slightly cooler on the beach and in the mountains.
The State Highway Administration predicted that motorists will roll about "500 million vehicle miles" this weekend, compared with 300,000 on a normal weekend. Gearing up for the holiday, she said, the SHA has deployed emergency traffic patrols to help travelers in distress, and roadside message signs and mobile radio- broadcasting equipment to inform motorists about road conditions and delays.
The SHA patrols will be equipped to call for emergency help, change a flat tire or even give away enough fuel for an empty tank to get the vehicle to the nearest gasoline station, said spokeswoman Liz Kalinowski.
There will be plenty of gasoline stations open, according to William F. Zorzi Sr., spokesman for the Mid-Atlantic branch of the American Automobile Association.
"Out of 30 key stations that we survey, 27 are going to be open," he said. "That's very unusual. It's never been this high."
Mr. Zorzi said the number of stations open was an indicator of plentiful gasoline supplies.
"We're swimming in it," he said, adding that fuel prices averaging $1.11.8 for a gallon of regular unleaded gasoline are about a penny less than Memorial Day weekend last year.
Nationally, Mr. Zorzi said, the AAA and U.S. Travel Data Center expect the heaviest travel for this holiday weekend in a decade, based on telephone surveys.
The motorist and trade organizations predict "continuation of what they call a vacation binge all summer," he said.
TIPS TO GET THERE
Idealistic travel writers might say that "getting there is half the fun."
But "getting there" could be the hardest part of a trip to the beach, with tolls collected only northbound on Interstate 95 and eastbound crossing the Chesapeake Bay Bridge.
Try to avoid peak traffic times, suggested Tom Fre- burger, Maryland Transpor- tation Authority spokesman. At the start of the weekend, the worst periods are 3 p.m. to 8 p.m. Friday and 6 a.m. to 10 a.m. Saturday.
On the return trip Monday, traffic builds up early in the day if the weather is bad and in the late afternoon other- wise. But at least travelers in Maryland won't have to stop for tolls heading south on I-95 or west across the bay.