Light snowfall in the D.C. region overnight created challenges for commuters Wednesday morning, as some schools closed and others announced delayed openings, airlines canceled flights and police closed a usually busy ramp onto the southbound lanes of the Baltimore-Washington Parkway because of downed wires in the roadway.

U.S. Park Police said the wires toppled overnight onto the ramp that leads to the parkway from Route 193 in Greenbelt. They are not sure when the ramp will re-open, as they are waiting on a repair crew.

Police warned drivers throughout the region to use caution because some roads are slick and icy.

Metro had troubles on four of its five lines Wednesday morning due to the extreme cold weather.

VRE sent an email alert Wednesday morning to its passengers warning that power is out at its stop at the L’Enfant Station at 6th and C streets SW. VRE officials said riders should use caution when getting on and off trains because the platforms are dark.

Schools are closed in Prince William, Stafford and Culpeper counties. Schools in Fairfax, Montgomery, Prince George’s, Howard, Frederick and Arlington counties, and in Alexandria, are opening two hours late.

Air travel has been affected by the latest round of snowfall. About 250 flights across the country were delayed and another 950 were canceled as a result of the winter weather, according to FlightAware.

Eighteen flights were canceled at Ronald Reagan National Airport. Another 15 were canceled at Baltimore-Washington International Airport, and four were canceled at Washington Dulles International.

For more transportation-related stories, click here. For updates on the Washington weather forecast, go to the Washington post’s Capital Weather Gang.