TIRED OF THE COOL air-conditioned comfort of your supermarket? Bored with the brave new world of hydroponics and cello packs? Puzzled by cucumbers fit for a wax museum? Don't recognize anyone on the runways at your favorite food store?

This is the weekend to forsake your supermarket for a spree at an open-air farmers market. It's harvest time and local vegetables and fruits are, ah, cornucopious. Throughout D.C. and the Maryland and Virginia suburbs, local farmers have transformed parking lots, parks, and sidewalks into gardens of earthly delights. The best of the summer's bounty awaits you: bushels of Silver Queen corn, vine-ripened tomatoes and unwaxed cucumbers; mounds of sweet cantaloupes, watermelons and ripe peaches; cartons of fresh brown eggs; jars of homemade jams and honey; buckets of freshly-cut flowers and fragrant herbs.

You just can't find better, fresher produce unless you grow it yourself or have a friend with a garden. But then you get zeppelin zucchini on your doorstep at 2 a.m. You can probably find better prices in the supermarkets, but do you really want to buy a cantaloupe from California? What you'll find at farmers markets that you won't find in your backyard or grocery store is that rare sense of community that flourishes when shoppers and farmers gather together in the open air.

"Sure, eggs may be cheaper in the store, but I'd much rather buy them here," says Ali Kahn, who shops at the Adams Morgan farmers market each Saturday. "One thing I love about the market is that you get a real feeling of community that makes Washington seem like a small town. You bump into some of the same people each week -- people speaking Spanish, French . . . a lot of shoppers are from countries where the market is a way of life. It's fun!"

Whether the market is in Adams Morgan, Southeast D.C., Takoma Park or Arlington, you'll find the same lively scenes: neighbors, friends and strangers ooh-ing and aah-ing over ripe peaches, sharing news about themselves and opinions about okra, meeting and talking with the farmers themselves -- the men, women and families who actually sow, harvest and sell their produce to you.

Most farmers who sell at the markets cultivate small tracts of land, from a few to a few hundred acres, in Maryland, Delaware, Virginia, Pennsylvania and West Virginia; they rely heavily on market sales for their livelihood. They are glad to see their customers and are eager to tell you, in so many superlatives, why their produce is the finest around. They'll tell you the day and time their corn was picked. They'll slice up a ripe melon for you to sample ("You won't find sweeter"). After you squeeze a few cantaloupes, they'll tell how to pick a ripe one (by the thickness or density of its netting). You'll pick up tips on ways to store, bake, fry, pickle, can or freeze what you buy. It's amazing how knowing the life history, previous owner and canning potential of a tomato can improve its taste.

Two of the many farmers eager to share what they know about their crops are Susan and Chip Planck, owners of Wheatland Vegetable Farms in Loudoun County. With help from their 16-year-old daughter, Nina, and a dozen college students hired for the summer, the Plancks bring their just-picked produce to farmers markets six days a week.

Lean, tan and enthusiastic farmers in their mid-40s, Chip and Susan knew little about farming before 1973, when they decided to put into practice the ideas about utopias and alternative institutions that Chip was teaching at the University of Buffalo in New York.

"Farming is a sensible and rational way of dealing with the world," says Susan. "We thought it would be nice, especially while our two children were still young. The market is one of the few places, except Chinese restaurants, where children make an economic contribution to the family. It's a great way to keep the family together."

So they moved to Virginia, and spent five seasons as partners of a farm near Tysons Corner learning the basics of growing produce and running a farm. In 1978 they purchased a century-old farmhouse on 60 acres in Purcellville and took up the hoe. They had plans to sell all of their first year's fruits and vegetables in that town of 2,000 people, but the demand wasn't as great as the supply: Purcellville did not fill their purse. Fortuitously, in 1980 new farmers markets opened in Washington, Arlington and McLean, giving the Plancks and dozens of other area farmers viable outlets. Today the Plancks sell 75 percent of their produce through farmers markets.

You'll find their stands popular and the produce attractively displayed. They take great pride in what they grow and sell. They choose varieties on the basis of taste rather than on suitability for shipping, long shelf-life, processing or mechanical picking. This means you'll see types of beans not sold in stores, cantaloupes the size of softballs and Big Boys that could star in "Return of the Killer Tomatoes."

With each variety of fruit and vegetable is a handwritten card giving its name and characteristics. Other signs say things you ll never see in your supermarket: PICKED FRIDAY 6 P.M. ASK FOR SAMPLE.

OUR FAVORITE.

And Wheatland Farms might have the only melon return policy around: If the cantaloupe you bought last week wasn t to your liking, they ll replace it for free.

You can meet the Plancks at their market stands or at their farm where they welcome visitors (and school groups in spring and fall) to view their fields, equipment, greenhouses and henhouse. You can buy "just off the farm" produce at their honor-system stand, venture into the fields to pick your own raspberries and visit the produce cellar where you can keep cool as a cuke while you choose between Silver Queen corn and Italian flat beans. But don t expect a guided tour; there are signs posted everywhere to make you feel at home and to direct you around the place. This is a working farm and the folks at Wheatland Vegetable Farms are doing just that.

For the Wheatland folks, 5:30 p.m. isn t quittin

time on Friday. They ve been up since 5:30 a.m., picking the produce for the Saturday markets in Arlington and at RFK Stadium. All day long, through rows of corn, across fields of tomatoes, and over quick meals, Chip, Susan and Nina call out their plans like football quarterbacks: how many bushels of corn go to RFK, who s assigned to pick raspberries, what truck gets loaded when, when to pick flowers, who can bunch beets, who needs a break.

Nina Planck, an equal partner in the Wheatland triumvirate, knows as much about corn, tomatoes, raspberries, market trends and crop yields as most high-school students know about Bon Jovi. She is energetic and glad to share her insights. "Every department store has lingerie, every market stand has to have tomatoes. You can t do without them," she declares as she picks her way through a plot of the beefsteak variety.

At 7:30 the truck loading begins and proceeds like clockwork. Quittin' time comes around 10:30. On Saturday morning around 4:30, Susan and two of the dozen students, leave in the dark for the Arlington Farmers Market. Chip and two others will leave shortly after that to set up at the D.C. Open-Air Farmers Market at RFK Stadium.

Susan will join about 50 other farmers, honeymakers, cookie and cake bakers in the parking lot of Courthouse Square. Before dawn they are busily setting up tables, unloading, arranging produce, making signs, hanging scales and plastic bags. Before the 7 a.m. bell starts business, shoppers are browsing and lining up to buy. Though surrounded by office buildings and construction cranes, you can hardly believe you re in downtown Arlington.

The market's crowded by 8; parking's impossible by 9. Elizabeth Montgomery, Arlington s jolly agent for the Virginia Extension Service which runs this market, acknowledges that it has nearly outgrown its space in Courthouse Square in the seven years it's been there. For the thousand who plan to shop here on Saturday, she has this advice: "Come early when it s easier to shop, or get dropped off by someone who will get a coffee and circle the block."

If you do come early, take a seat on a bench near the market entrance, sip your coffee, and enjoy. If you re lucky, A. B. Groves from Smithfield Farms will be there. He s farmed all eight decades of his life. He s been at the market since about 1 a.m., helping his son set up a rather elaborate "slow load" produce stall they drove up from Oak Grove, Virginia. At 5:30 Saturday morning, he s talking and joking with other farmers. ("Ain t anything tastes like it used to anymore." "How many thousand dollar bills you got with you today? Just a hundred?")

If asked, he ll tell you that the A in A.B. stands for "Algernon. Ever heard that name before? Know what it means? The dictionary says it means 'lover.' " Pause. Grin. "Lover of money." (If you want to know what the B stands for, you'll have to ask him yourself.)

Good humor prevails at farmers markets. Consumers feel good about buying their fruit and vegetables from people such as Groves and the Plancks, who are generous with their time. Farmers like to meet the people who buy and enjoy their produce. In these days, as supermarkets introduce "high-touch" scoop-your-own-granola bins to compensate for the lack of human interaction, we need farmers markets.

In Washington that need was answered in 1980 by the D.C. Open-Air Farmers Market held in Parking Lot 6 of RFK Stadium in Southeast. In its seventh season, it is the largest and liveliest in the area. On a typical Saturday, more than 12,000 people browse and shop at the tables set in the curve of shade under Metro s elevated tracks.

Al Smith, executive director of the D.C. Federation of Consumers and Farmers Markets, Inc., is the driving force behind this market. You ll find him at RFK each Saturday, talking with farmers and customers, picking up discarded melon rinds ("liabilities," he calls them), catching up on gossip and making announcements over his megaphone about lost or found car keys.

"The market represents the great natural marriage of urban and rural," says Smith, the proud matchmaker. "It has a lot going for it. It s near the Stadium-Armory Metro stop, there's plenty of free parking, it's convenient to the low- and middle-income families of the area and to farmers who truck in their farm goods from Routes 50 or 295."

More than 30 producers and vendors hawk their wares here. About half the farmers at RFK produce what they sell. The other half sell produce of other growers or wholesalers. While wholesale fruits and vegetables can be bought at lower prices, some of the "producers-only" advocates feel that the quality of these goods is lower as well, since they may not be selectively picked or carefully handled. The beauty of this market is that it offers the best of both worlds: Purists can pay a bit more to look the producer in the eye when they buy, and those who like to look anyone in the eye can save some money. It beats anonymous shopping any day.

If you are considering getting out in the open air of the farmers market, you have plenty of choices around the city. Even if you buy just a couple of peaches, you'll have a great time browsing and chatting. Plan to linger. Only by lingering will you get to talk or listen to people like Southeast resident Mary Brooks. She comes to RFK every Saturday for her produce. Today, Brooks is standing at a table piled high with peaches, scrutinizing each piece of fruit for her annual canning. She carefully fills her shopping bag with enough to last her through the winter. When asked why she chose this particular table, she casts her eye around to the other tables and whispers confidentially, "This stand is really beautiful." TO MARKET, TO MARKET

WASHINGTON

ADAMS MORGAN FARMERS MARKET --

(783-7726) 18th and Columbia NW (the plaza at Perpetual American Bank); Saturday 7 to 6, year round.

ALL SOULS MEMORIAL EPISCOPAL CHURCH --

(232-4244) 2300 Cathedral Ave. (off Connecticut) NW; Saturday 9 to 2 until late October.

D.C. OPEN-AIR FARMERS MARKET --

(678-0610) Parking Lot 6, RFK Stadium (Oklahoma and Benning roads NE); Tuesday and Thursday 7 to 6, Saturday 6 to 3 through Christmas Eve.

EASTERN MARKET --

(546-3524) Seventh Street between North Carolina and C streets SE; Saturday 7 to 6 year round.

GEORGETOWN BURLEITH FARMERS MARKET --

(678-2800) 35th and Wisconsin NW (across from Safeway); Saturdays 9 to 2 until Thanksgiving.

MARYLAND

MONTGOMERY FARM WOMEN'S COOPERATIVE MARKET --

(652-2291) 7155 Wisconsin Ave., Bethesda; Wednesday and Saturday 6 to 4 year-round.

MONTGOMERY COUNTY FARMERS MARKETS --

(251-2345) operates out of three different locations through pumpkin season in late October:

Bethesda: National Institutes of Health, 9000 Rockville Pike, Parking Lot 41B; Tuesday 3 to 6.

Gaithersburg: Bureau of Standards, Parking Lot 235, off Quince Orchard Road; Thursdays 3 to 6.

Silver Spring: Armory (1 block off Georgia Avenue at Pershing and Fenton streets); Saturday 8 to 1.

PRINCE GEORGE'S COUNTY FARMERS MARKET --

(868-8783) Wells/Linson Complex, 5211 Calvert Rd., College Park; Saturday 7 to noon through September 26, 8 to 1 through October 24. Eleven producers.

TAKOMA PARK FARMERS MARKET --

(270-1700) Laurel Avenue and Carroll Street; Sundays 10 to 2 through November.

VIRGINIA

ALEXANDRIA FARMERS MARKET --

(838-4770) Market Square at City Hall in Old Town (301 King St.); Saturdays 5 to 9 year-round.

ARLINGTON FARMERS MARKET --

(558-2475) Courthouse Square, N. Courthouse Road at 14th; Saturdays 7 to noon through November 28.

FAIRFAX EXTENSION FARMERS MARKET --

(691-3456) Thaiss Park, 3400 block of Picket Road, between U.S. 50 and Rte. 236. Wednesday 9:30 to 2 through November 4.

FALLS CHURCH FARMERS MARKET --

(241-5027) Falls Church City Hall (on the corner of Little Falls and Park avenues one block north of Route 7); Saturday 8 to noon through October 31.

McLEAN FARMERS MARKET --

(759-2119) at McLean Baptist church on Chain Bridge Road at Brawner Street; Friday 8:30 to 1 through October 31.

MOUNT VERNON FARMERS MARKET --

(691-3456) Mount Vernon District governmental center, Parkers and Sherwood Hall lanes, (behind the fire station); Tuesday 9 to 2 through November 24.

RESTON FARM MARKET --

(759-7272) 10800 Baron Cameron Ave.; Monday through Saturday 9 to 9, Sunday 9 to 8:30, April through December.