With icy temperatures and promises of scattered snow flurries, many area shelters are adding beds and hours to offer a warm Christmas for the area's homeless.

In the District, emergency shelters opened for the third night in a row last night and probably will stay open through the weekend. Many Maryland and Virginia suburbs expect a rise in the number of people seeking shelter over the holidays.

Today's temperature will feel as though it's in the teens because of a wintry breeze that will keep light snowflakes flying, according to a forecaster at the AccuWeather Service. On Christmas, the high may reach 34 degrees before the windchill factor kicks in.

Once the temperature or windchill factor is 32 degrees or lower, District shelters open overnight to anyone who comes, said Jean Barton, lead shift supervisor for the D.C. Hypothermia Hotline. Last night, she was at the D.C. Village shelter for families, where 15 families had taken refuge.

In Fairfax County, where the homeless often seem invisible, shelters reach capacity too quickly, sending handfuls of homeless people back to the cold, bitter streets, said Pam Michelle, executive director of New Hope Housing.

"This is when people who have been out all year finally begin coming into the shelters," she said. "They just fill up real quickly, but we have an overflow program with extra trailers where some can stay. Even so, we're at 100 percent capacity."

Because the District has been on hypothermia alert since Tuesday, the Reeves Municipal Center at 14th and U streets NW also has been open for single men. A homeless person may call the hypothermia hot line at 1-800-535-7252 to find out if the Reeves Center or D.C. Village, both all-night shelters, is open or to get a ride to one of the city's seven emergency shelters.

In addition to picking up those seeking rides, vans cruise the city looking for homeless people to encourage them to consider a warm bed for the night.

In Maryland, social service agencies determine daily whether to open more shelters and what services will be needed, based on temperatures. Most counties expect a rise in the number of people seeking shelter over the Christmas weekend.

Montgomery County officials said they may keep all six emergency shelters in the county open during the day if the temperature dips to 20 degrees or below. The homeless usually must leave shelters by 7 a.m.

The shelters--one for single men, two for single women and three for families--provide 165 beds. Officials said the county also may open a shelter at Progress Place in downtown Silver Spring for use during the day.

In Northern Virginia, shelters already have added beds this winter to accommodate the growing number of people seeking refuge.

At Carpenter's Shelter in Alexandria, a few extra cots were added to the 80-bed overnight facility. At the Arlington Street People's Assistance Network (A-SPAN), room is being made, but many people still are turned away, said Marte Birnbaum, director of the Operation Place, a branch of A-SPAN.

Paul Heimer, with the Northern Virginia Coalition for the Homeless, said area shelters prepare for the influx of transients by adding beds or referring people to a place that can house them overnight.

Andy Carpenter, spokesman for Anne Arundel County Executive Janet S. Owens (D), said officials were prepared to open two county-run shelters through the weekend. When temperatures dip below freezing, he said, county police are dispatched to areas where homeless people gather to tell them where to find shelter.

In Montgomery, those seeking shelter day or night may visit or call the Montgomery County Crisis Center at 301-315-4000. County residents also may call to report someone they believe needs shelter or other help.

Social service officials in Prince George's County said the county has a 100-bed shelter for women and children and 13 apartments available for homeless families. A men's shelter also is open at Prince George's House.

A program called Warm Nights, a collaborative effort by local churches, nonprofits and Prince George's County, also offers shelter and hot meals. Each week, two of the more than 100 participating churches open their doors; a local nonprofit supplies beds and linens.

Those seeking shelter in these must call 1-888-731-0999 to reserve space. A van is available for pickups.

"I don't think we're anticipating any more homeless over the holiday," said Karyn Lynch, director of the Prince George's Department of Social Services. "This is the time of year I would imagine a lot of people take family members in."

In the end, it is often up to the homeless to determine where they'll sleep.

At the McPherson Square Metro station in Northwest Washington, Dwayne Howard sat on a crate reading a newspaper before retiring to a park for a night's sleep. Howard, 39, said he will spend Christmas Day with his mother, who lives in a senior citizens home.

"But I'll sleep in the park. I stay out at night," said Howard, who said he has been homeless for five years. "I don't like shelters because they're dangerous places, and I can't stay at my mother's [home]. I have five blankets. I sleep on two and put three over me."

Staff writers Scott Wilson and Jamie Stockwell contributed to this report.