Bone-chilling cold has Sonoma County social service providers scrambling to provide shelter for those most vulnerable: folks without homes.

A spate of freezing nights that are expected to continue through the weekend in some areas warrants attention on everyone's part, whether to safeguard pets and livestock, keep back yard plants from freezing or avoid driving on icy roads.

Wet weather forecast for Friday — even with meteorologists withdrawing predictions of snow — increases the risk of hypothermia, enhancing the urgency for providing of shelter for those without, providers said.

A change in the weather can be a matter of life or death for the estimated 3,300 county residents accustomed to sleeping outside, according to the last countywide homeless count.

"When you stack the rain on top of the cold, then it gets really dangerous because you can't really get warm when everything's damp," said Mike Johnson, chief executive for the Committee on the Shelterless in Petaluma.

Temperatures early Thursday dropped to 20 degrees in some areas of west Sonoma County, and hovered in the low and mid-20s elsewhere, the National Weather Service said.

The coldest community in the area appeared to be Graton, at 19 degrees, meteorologist Steve Anderson said. In Napa County, the airport came in at 16 degrees, however.

At the Charles M. Schulz-Sonoma County Airport north of Santa Rosa, the mercury hit 24 degrees, matching the record from Dec. 5, 1972 at the previous downtown Santa Rosa data collection site, according to the National Weather Service.

Overnight lows are forecast to be in the 20s and low 30s until at least Tuesday night — warming slightly for a bit of rain Friday afternoon and Friday night —- then slowly warming a few degrees a day after that, the weather service said.

Social service agencies have added capacity for 102 more people in local shelters that already provide 584 beds year-round, said Jenny Helbraun Abramson, who coordinates planning for homeless services in Sonoma County. That's about a 17 percent expansion this week, she said.

An impromptu warming center pulled together at the last minute Wednesday night at the Santa Rosa Homeless Services Center run by Catholic Charities provided a glimpse of people who found themselves out in the cold and in need of help.

For the first time, the organization's day-time drop-in center extended its operations through the night to provide a place for people to warm up as temperatures dropped into the teens. Among them was a man who reported waking up outside in the dark of early morning covered in frost.

Volunteers who stepped up on short notice and donors who came through with tents and heaters offered light in the dark for about three dozen people who took advantage of the warming center, said Jennielynn Holmes, director of shelter and housing for Catholic Charities.

"We just kind of pulled it off at the last minute, and we expect about double that tonight," she said Thursday.

More people came Thursday morning, some of them "shopping" for warm duds among the donated clothes, others enjoying hot coffee and oatmeal.

Lodi Goro, 27, and her 11-week-old puppy, Roma, were among those drawn by the promise of heat. "This is kind of awesome," she said early Thursday, noting that having so many familiar faces from among her homeless friends together made it special. "It's a community thing."

"I'm glad to have this place going for the homeless people who need help," said another, Michael Thavaong, 33.

Holmes said it was uplifting to have donations come in from individuals and businesses — some unsolicited — allowing organizers to set up a patio heater, two large camping tents and a canopy shelter, and to offer coats, hats, gloves, socks and other cold-weather apparel.

Volunteers stayed through the night, serving up soup and coffee. They were assisted by some from the homeless community who came to get warm and helped out

Dave Meyer, 55, who cooks at the St. Vincent de Paul Society mission, said able-bodied people in the homeless community are eager to help those less fortunate.

"It was amazing how respectful everybody was," said Kimberly Jo Smith, a volunteer helper who was once homeless herself. "The donations we are getting are just overwhelming," she added.

Holmes said an additional patio heater and at least one more tent were being donated Thursday, and that blankets, sleeping bags and warm clothing were still being accepted at the Family Support Center, 465 A Street, in Santa Rosa.

"We're really just trying to keep people alive," she said.

(You can reach Staff Writer Mary Callahan at 521-5249 or mary.callahan@pressdemocrat.com.)