The air is warm, the moon is high, and you're in love. It's the perfect summer romance.

Snap out of it.

Not that we don't believe in love. Love is a fine thing, but summer romances can turn healthy, normal adults into whimpering, lovesick wrecks by Labor Day. This is especially true in Washington, where thousands of fresh-faced singles swoop into town for summer internships. Eyes meet, hormones flare, and suddenly one morning two people wake up with matching heart tattoos.

One could spend the whole summer safely huddled in the office, but what fun is that? No, it's better to lather on SPF-15 and join the party. A summer fling can be delightful--if you follow a few simple rules:

Rule 1: This Is Temporary.

The good news, and the bad news, about a summer romance is that it has a finite time frame. For some lighthearted Romeos and Juliets, this is the perfect formula: footloose, fancy-free and--best of all--leaving at the end of the summer.

"Nothing serious," says Page Homberg, a 21-year-old senior at American University. "If you know there's a time constraint, then you can just enjoy yourself. I'm not looking for a serious relationship. I'm just trying to have a good time."

It's party time, romantically speaking. Everybody is a little more relaxed. People are away from their daily routines and responsibilities. The boyfriend or girlfriend back home is . . . well, back home. Real life is on hold for three months.

"It's a summer attitude," Homberg says. "It's more carefree."

Summer romances, like vacation flings and other short-term dalliances, thrive because of their low potential for risk. No expectations. Carpe diem. No nasty breakups.

Terri Berwick, a 27-year-old lawyer, spent last summer in San Francisco, where there was a different festival every weekend--the primo spot for singles to meet and mingle. Berwick met a ton of guys.

"It was a free-for-all," she says. "Everybody meeting everybody, but nobody was serious."

Rule 2: Keep It Light.

While most folks are carefree and casual, more romantic souls fall hard and fast. A summer romance can be, in an odd way, much more intense and intimate.

Think airplanes. You plop next to a nice-looking fellow in 16-D, and minutes later you're pouring out your deepest, darkest secrets to this incredibly sympathetic stranger. Why? Because after the plane lands, you'll never see him again. Summer romances work the same way. People are much more open and honest with strangers because they have less to lose.

"I think the time constraint can be a virtue," says 20-year-old Cheri Cox. "It speeds things up. There's less game-playing."

He's connecting, she's bonding. They're sharing hopes and dreams. No waiting three days to call. None of this "Let's take it slow and see what happens." Time's a-wasting. The normal trajectory of romance is compressed into hours and days instead of weeks and months.

Pals Katie and Michael, two twentysomething veterans of failed summer flings, said things get way too deep way too fast.

"There's an intensity there to capture the few moments you have," he says. "That tends to escalate the emotions past where the relationship really is. It's like the bulls of Pamplona: You just go down that street."

So, nothing too heavy, please. Maybe you've found your soul mate, but it's impossible to know under the heady influence of sun, heat and those lingering, late-night conversations over margaritas.

Rule 3: Don't Confuse Lust With Love.

Speaking of margaritas, we should mention that old devil Lust.

Summer is a sexy time. The days are longer and the sun is brighter, which means that hormones kick in big time. People wear less clothing and sweat more, which activates all those biological impulses.

Which is one way of saying that people who wouldn't give you the time of day in November are suddenly hot to trot. Too many people confuse this sudden urge to merge with True Love.

"It's all about hooking up," Katie says. "There's no relationships beyond a weekend."

That's not entirely true. But many a heart has been sunburned when one partner thought this summer romance was the real thing, and the other thought it was just a really hot fling.

Rule 4: Think Friendship.

Okay, summer's over. It's time to go home. The proper way to end a summer romance is this: one tender, quick kiss and a promise to stay in touch.

You do not bombard the newly departed love with e-mail, phone calls or love letters. You may do any of these things once. But then you must wait for a response before writing or calling again.

Some summer romances transform into genuine friendships or even something more. But you shouldn't count on it. Lack of proximity, old friends, school and jobs are now competing for time and attention--not to mention boyfriends and girlfriends on home turf.

Even when there's no romantic competition, the very traits that made you a perfect summer partner may sink the chances of long-term love.

Last summer, the fact that Terri Berwick lived in Washington made her a safe bet in San Francisco. By September, that was a problem. "I became what was known as GU: Geographically Undesirable," says Berwick with a laugh.

Rule 5: You Never Know.

Sometimes summer romances actually last. Summer slips into fall, and somehow both people still want to be together. Some folks move to be near the one they think they love. Some people even marry their summer romance.

Keep an open heart and never say never. Heck, you might win the lottery, too.