The villain was a near-gale-force squall moving out of a low pressure pocket off the Atlantic coast. It sucked a cold front right out of eastern Canada and across the Washington area Sunday night, stirring up winds that toppled trees, cut off electric power in thousands of homes, threatened early spring gardens and chilled hard-won spring fevers into a crazy quilt of goose bumps.

The cold front had plunged into north Florida by yesterday afternoon. But the winds unseasonal cold - and the general sense of having been ambushed - lingered here. The storm, arriving at about 11 p.m. Sunday, had punctured a Mother's Day of shimmering blue skies and kite-perfect breezes.

But yesterday, ill-prepared pedestrians in scanty spring clothing leaned into the wind like sailors in a storm. "My winter suits are all in storage!" huffed one professional man.

The bizarre pattern also gave southern California a record rainfall and sent snowplows out of storage in the northeast to clear away a six-inch fall in some sections. In the Washington area, the winds gusted to 70 miles an hour.

"These winds are not so rare here, but they usually last only a couple of hours at a time; what is unusual is that they lasted so long," said Charles Chilton, a forecaster for the National Weather Service. He said forecasters had underestimated the intensity of the Mother's Day squall and had not seen it coming until it was almost here. "I myself was off duty," Chilton noted.

The temperatures, which reached a high in the high 50s yesterday, were expected to dip overnight last night into the upper 30s in the suburbs and into the low 40s in the city.

The Virginia and Potomac power companies had extra crews working around the clock to repair downed power lines. According to spokesmen for the two companies, 15,000 to 17,000 customers in northern Virginia and about 5,000 in Washington and the nearby Maryland suburbs were without power at some point. New reports of power failures were still coming in late yesterday.

Sections of several streets in Northwest and Southeast Washington were temporarily closed early yesterday while road crews cleared away fallen trees and limbs. The streets were reopened before the morning rush hour, a police spokesman said.

A woman visitor from West Germany was injured yesterday morning at the Washington Monument when the wind blew a piece of plywood loose from a construaction site at the Mounument's base, according to Mary Krug, of the National Park Service. The woman was treated for head lacerations at George Washington Hospital after she was struck.

The Park Service had closed the grounds, as it always does when the winds are high, Krug said, but the woman apparently did not see the signs.

"I don't know why, but the wind currents are really bad around there," Krug said. The Park Service had to use a truck to get its own personnel out of the Monument Sunday night, she said. "The wind was so bad, it took two people to get the truck door open."

The storm was especially hard on trees, according to horticulturists. The ground had been softened by rains a day or so earlier, making it easier for the wind to uproot them.

The damage to trees in the area of the Mall and other monuments alone is estimated at $25,000 to $30,000, according to Oscar Livingston, a Park Service horticulturist.

Livingston cautioned citizens to beware of "hangers," broken limbs still aloft in trees but hard to spot. He advised against walking or stopping to talk under trees for the next days, particularly when the wind is gusting, until after work crews have had a chance to clear them.

For those home gardeners whose newly planted vegetables and flowers were not squashed by a fallen oak, Livingston and other horticulturists in the area said there was hope.

"The wind presents the most danger to newly planted annuals fresh from greenhouses. They haven't had time to harden up yet and the wind is liable to snap them off," Livingston said. "Luckily we (the Park Service) haven't planted our annuals yet. It's established around here that you're not really safe until May 15, and there is some risk even after that (of a frost, or snow)."

Plants close to the ground, such as strawberries, are safe, unless there's a frost, he said.

The record low for a May 9 is 34 degrees and for a May 10, 35 degrees, according to the Weather Service. The low yesterday was 40 degrees at 5:40 a.m.