A dank and soppy Saturday dissolved into a cool, crisp and cloudless afternoon yesterday, leading October into a teasing cycle of warmth alternating with chill.

After rising to an afternoon high of 60 degrees yesterday, temperatures were to drop during the night to between 34 and 40 degrees for the coldest day of the season so far, according to the National Weather Service. The normal high for the date is 74.

The sudden cold resulted in a strain on the District's shelters for the homeless, a spate of house fires in the city Saturday night, a rush of calls to furnace-servicing firms and renewed trade in some cold-weather items during the weekend.

Clear and sunny weather, with high temperatures back up in the low to mid-70s, is predicted for today and tomorrow. Then, late tomorrow or Wednesday, "we go through the whole thing of {Saturday} again" with more rain, said Weather Service specialist Joseph Cefaratti.

All in all, October "looks like a pretty fair month," with precipitation and temperatures expected to be normal, Cefaratti said. The average daily high for the month is 68.9 degrees, and the average low is 49.7 degrees.

Saturday's cold resulted in a number of residential fires in the District because of faulty furnaces and fireplaces, and companies that service furnaces reported receiving a burst of calls for emergency service.

A two-alarm fire broke out at 1410 34th St. NW, causing an estimated $500,000 in damage but no injuries, when dried-out flooring next to an old fireplace ignited, according to the D.C. Fire Department. A fire at 1312 Columbia Rd. NW apparently started from a kitchen stove being used to heat the house, firefighters said. And three firefighters were treated at Washington Hospital Center and released after they were injured at a blaze at 1161 Morse St. NE that was attributed to a faulty furnace.

"This always happens with the first cold wave," a D.C. fire official said. "When cold weather hits like this, people start cranking on their furnaces and fireplaces that weren't used for six or seven months."

Charles Pursey, service manager at Steuart Petroleum Co., said that his firm is getting "an exceptional amount" of service calls for this time of year and that the company has had to call in extra staff to handle emergency service.

Several of the city's homeless shelters filled up Saturday, and shelter directors said this did not bode well for the winter.

"Frankly, I'm very nervous about the winter. We don't usually start out the winter absolutely full," said Judy Goodenough, coordinator of the Luther Place emergency shelter for women at 1226 Vermont Ave. NW. The center, which normally sleeps 32, accommodated 50 for dinner Saturday night with 38 women staying overnight.

The 60-bed Gospel Mission at 810 Fifth St. NW and the 110-bed shelter run by the Community for Creative Non-Violence at Second and D streets NW had to turn people away.

The Saturday night chill was enough of a winter foreshadowing to send some families off shopping for cold-weather needs yesterday.

Outside a jammed Hechinger store at Baileys Crossroads, Judy Sherman of Arlington was loading logs and furnace filters into her car. "We froze last night," she said, adding that she planned to have her first fireplace fire of the season last night.

Dean Masajada, assistant manager of the Grate Home & Fireplace store in Springfield Mall, said that Saturday "was the busiest day since last winter," though yesterday was slow.

On the Mall downtown, meanwhile, more people wandered out as the afternoon wore on to walk or picnic or play football. While the ice cream vendor at the Washington Monument termed business "slow," the crowd circling the monument was about average for this time of year, with a 40-minute wait to get in, according to guides there.

While the erratic weather may make an irritating guessing game out of getting dressed each morning, it may prove a boon to fall colors. Leaves should start changing color in a week or two, and the periodic rain should make them brighter than last year, when dryness turned them brown, Cefaratti said.

Staff writer Sari Horwitz contributed to this report.