WHAT do you do when it's too hot for 18 holes of golf? Play miniature golf, of course. And when it's too hot for miniature golf? Wait until sunset.

Most area miniature golf courses have after-dark hours and lighted ranges, and, this time of year, there's no better time to hit the links than when the air cools and fireflies light the edges of the course. Late hours also mean that even after school starts young golfers can keep up the pars they've worked on all summer.

There's even a tourney for nocturnal mini golfers, the third annual Putt-in-the-Dark Night Mini-Golf Tournament, held at Jefferson Falls Park in Falls Church on Sept. 8. For one night only, they'll turn off all the lights at the park's miniature golf course -- even the ones that usually turn the blue-dyed waterfall into a magnificently glowing fantasy. Each contestant gets a glow-in-the-dark ball, which he or she must putt into holes lit only by the glowing light sticks stashed inside. But not to worry: Course staffers will be on hand to guide golfers from hole to hole by flashlight.

Besides, admits tournament organizer Laurie Scott, "It's not that difficult because we're right next to the parking lot, which is all lit up."

There's plenty of time to practice your p.m. putting in the interim. One of the most dramatic mini golf courses in the area, at Upton Hill Regional Park in Arlington, is even more so at night. The course is arranged so that its numbered greens -- skillfully designed for challenging shots -- work their way up and around a small hill. Waterfalls flow into an intricate system of waterways that run between the greens, forming water hazards for some, and empty into ponds filled with water lilies and goldfish.

The pie{grv}ce de re{acute}sistance at Upton Hill is Hole 10, which features a green that slopes 140 feet to the hole. Awesome. This hole was reputed to be "the longest in the world" when the course was designed in 1990, but since then the mini golf course at Rocky Gorge Golf Fairway in Laurel has nabbed that superlative with a 190-foot hole.

Most courses in the area are "resort style," which means they have an emphasis on landscaping and challenging green designs that mimic more serious, full-size ranges. Founded in 1964, Rocky Gorge is one glorious exception to the rule, with its singing evergreen tree with moving eyes and mouth, a singing cowboy, a model Washington Monument and a clown with a lighted nose. Despite such distractions, Rocky Gorge's challenging greens demand attention. And do they get plenty of night duffers? You bet!

"It's entertainment," Rocky Gorge owner Gus Novotny says. "We're competing with television, the movies and everything."

Both Upton Hill and Rocky Gorge are lit by floodlights high overhead, which keep insects away from the golfers, and both have spotlights on key features. The deeper shadows give the courses an air of mystery. And there are no colored lights to distract players, as there can be at beaches or resorts. "The color comes from the place itself," Novotny says.

Of course, you won't get on the PGA circuit by knocking a ball into a clown's mouth or over a replica of the Golden Gate Bridge. But that doesn't mean mini golf is athletically valueless. Woody Fitzhugh, the owner of Woody's Golf Range and a former touring PGA professional who designed his mini golf course himself, puts it best: "Any time you're putting at a hole, you're helping your golf game."

PUTT-IN-THE-DARK NIGHT MINI-GOLF TOURNAMENT -- Sept. 8 at 8 p.m. at Jefferson Falls Mini-Golf, 7900 Lee Hwy., Falls Church. 703/573-0443. Age divisions for this singles tournament are 4 to 6, 7 to 9, 10 to 12, 13 to 15 and 16 and up. Prizes and trophies will be awarded to the top two in each age group. Reservations are required by Saturday; rain date is Sept 15. $12 per player.

AREA COURSES The miniature golf course at Upton Hill Regional Park in Arlington winds through waterfalls and across bridges.