Kenosha, Berthoud and Loveland passes remain closed overnight because of bad weather.
Motorists were encouraged to avoid mountain travel if possible, because a snowstorm was expected to continue into Tuesday, said Amy Ford, spokeswoman for the Colorado Department of Transportation.
A winter storm warning remained in effect until early Tuesday morning for the northern half of the state. Snow was falling overnight in the Denver metro area.
Here are key closures around the state:
U.S. 285 was closed over Kenosha Pass because of adverse weather at 3:20 p.m.
U.S. 40 Berthoud Pass was closed at 1:05 p.m. because of severe weather and potential avalanche danger. CDOT said the highway would be closed overnight.
U.S 6 Loveland Pass was closed at 11:51 a.m. because of adverse weather conditions.
In metro Denver, eastbound Interstate 270 to I-70 was closed because of accidents at 9:36 p.m.
In Douglas County, a multi-vehicle wreck closed northbound Interstate 25 at Surrey Ridge from 6:43 p.m. to 8:35 p.m., CDOT said.
For more information call or visit 511, or go to the website COTrip.org.
CDOT crews werey working around-the-clock snow shifts along the I-25 and I-70 corridors, Ford said. Snow shifts last 24 hours a day, from noon to midnight and midnight to noon.
CDOT has between 60 and 75 plows working in the northern mountains, 30 to 40 along the I-70 Mountain Corridor, and about 120 to 130 plows across the Front Range and Eastern Plains.
Interstate 70 at Vail Pass reopened Monday evening after being closed in both directions for several hours.
Eastbound I-70 at over Vail Pass reopened at 6:42 p.m. after being closed for more than seven hours. Westbound I-70 over Vail Pass reopened at 5:26 p.m. Monday after a nearly five-hour closure.