Bicycle messenger Prentice Treadwell maneuvered through downtown Washington yesterday, his body covered from cap to boots except for a patch of forehead peeking out above his goggles. He insisted that working outdoors in freezing weather is no big deal -- if you've got the right winter wardrobe.

"People seem to complain about the cold, but I'm used to it," said Treadwell, 29, whose "regular winter riding clothes" included a blue leather ski mask, thermal underwear, a three-layered jacket with a polypropylene lining, nylon pants and ear muffs.

But most Washingtonians ventured outside as little as possible as area temperatures dropped to a low of 11 degrees and never climbed above 20. The windchill factor was between 2 and 10 degrees below zero.

Temperatures are expected to edge up today into the low 20s. The region also is likely to get its second snowstorm of 1988, one that could dump four or more inches, according to a winter storm watch issued by the National Weather Service. Forecasters said there is a 30 percent chance the snow could begin falling by late afternoon, and that snowfall was virtually certain by 10 p.m.

That weather system already has belted northern Arizona and New Mexico, Utah, Colorado, Kansas, Oklahoma, Missouri, Arkansas and northern Mississippi with wind and snow. The current cold spell gripping the Midwest and the Northeast has been blamed for 22 deaths, including 14 from exposure.

The Washington area's bitter cold weather caused cracks and leaks in small water mains in Arlington County, affecting service to houses in about 20 blocks, according to a county water and sewer spokesman. In Montgomery County, Potomac Electric Power Co., the county's major electricity supplier, said increased demand caused a 15-minute power outage to about 150 houses in Bethesda.

Another power failure left students at Jones Lane Elementary School in Darnestown without heat until midmorning yesterday. Classes were not canceled.

A Pepco spokesman said the company, which serves 600,000 customers in the District, and Prince George's and Montgomery counties, set a record for winter peak usage Tuesday of 3,950 megawatts, but had no trouble meeting the demand for power. Virginia Power said customer demand approached record winter levels of 10,700 megawatts yesterday morning and could break all records today as the cold weather continues.

The weather has not been cold enough yet to freeze the Potomac. But the cold spell has caused ice to form in the shallow parts of the river here, according to the National Weather Service.

The Potomac area American Automobile Association was even busier than Tuesday, fielding about 200 calls an hour yesterday, most of them from motorists with dead batteries who needed a jump start.

"We've serviced 1,800 calls, and we're projecting it may go as high as 2,600 to 2,800 by the end of the day," said spokeswoman Laura Martinez. "The record was 3,200 calls in January 1985, but maybe by the end of this cold snap we'll hit a record."

The cold temperatures snapped a Metro subway rail in two places on the Orange Line early yesterday, delaying morning commuters. A break in the rail between the Dunn Loring and Vienna stations was repaired by 6:15 a.m., and another break between the New Carrollton and Landover stations was fixed by 8:15 a.m. Metro ran trains in both directions along a single track during the repairs, and has stepped up inspections of the rail, said spokeswoman Marilyn Dicus.

The deep freeze that kept most people indoors also created the need for expanded emergency services for those who live on the streets.

The District said 40 homeless people spent Tuesday night in the District Building, whose ground floor was opened to them a few hours after the D.C. Council gave the go-ahead. An additional 60 persons spent the night at the Randall School building in Southwest.

Prince George's County officials, reacting to forecasts for several additional days of extremely cold weather, said they will not enforce a five-day limit on the length of time homeless families and individuals may stay in area motels under contract with the county to provide emergency shelter.

Paul Bifoss, the county's resource development coordinator for the homeless, said Prince George's has made no provisions to open county buildings to the homeless because social service workers "have not been inundated with requests for such services."

About 800 Montgomery County residents in Germantown lost power about 4 a.m. Tuesday when an underground cable burned apart because of increased demand. Jim Latimer, an official at the Potomac Edison Co. in Frederick, which serves about 20,000 customers in northern Montgomery, said power was restored by early Tuesday afternoon and that no one was without electricity yesterday.

At the Margaret Schweinhaut Senior Center in Silver Spring, the busiest in the county, director Barbara Dahlman said a normal number of elderly showed up yesterday, but they worried about the expected snow.

"They really like coming here, but they won't come out in the snow," she said. "They're afraid of falling."

In Fairfax County, about 200 households reported frozen pipes. There were also breaks in two small water mains affecting service to several blocks, according to a county spokesman.

For Joanne Navickas, a U.S. Postal Service letter carrier who walks a six-mile route in Fairfax City, the cold weather means cracked and bleeding hands.

"You can't work the mail with mittens," she said, holding out a hand riddled with small cuts. "You have to be able to finger the mail to sort it. I wear a half glove on my right hand."

United Parcel Service deliveryman Don Scarano, 31, of Springfield wore long underwear as he dropped off packages in Alexandria's Old Town. But he, too, has a job-related handicap in cold weather. "Fifty percent of my job is writing, so I can't wear gloves." Staff writers John Ward Anderson, Patricia Davis, Paul Duggan, Retha Hill, Evelyn Hsu, Virginia Mansfield and Caryle Murphy contributed to this report.