Fierce winds swept a cold front through the region last night, downing tree limbs and power lines, snapping some utility poles and wreaking havoc with sensitive home alarms, especially in Northern Virginia.

The gusts, 35 to 40 mph at points, kicked up about 6 last night and lasted about two hours as the cold rushed in and temperatures fell to the 20s in the District and to the teens in some suburbs.

For a time last night, more than 4,000 customers were without power across Northern Virginia, mainly in Fairfax County and the Woodbridge area of Prince William County, according to Dan Genest, a spokesman for Dominion Virginia Power.

The winds were strong enough to snap a handful of utility poles in parts of Fairfax County.

By midnight, all but about 1,000 customers had their power restored, according to Genest. He said crews will be out today to repair the broken poles.

Pepco's Web site reported only sporadic outages in the District and parts of Maryland.

Fairfax County police said they were called to quiet more than a few home alarms that were triggered by the heavy winds, which settled down late last night to about 10 to 15 mph.

The cold, however, remained.

The high temperature today is expected to hover around 38 degrees.