Colorado was hit with its first significant storm of the season Sunday, bringing heavy snow to some parts of the state. The National Weather Service issued winter storm warnings for much of northern and central Colorado as some towns reported snowfall of more than 18 inches.

Eighteen inches of snow accumulated in the Colorado resort town of Steamboat Springs, the Associated Press reported. The town of Red Cliff, south of Vail, reported 14 inches of snow, while Winter Park saw almost 10 inches. Interstate 70 was closed Monday and travelers were urged to stay off the road: the state opened some shelters to accommodate those who couldn’t travel.

Early season storms typically bring heavy, wet snow, according to the Weather Channel. Such snow often downs power lines and topples trees. Thousands of people in the state lost power as a result of this particular storm: about 21,600 customers lost electricity starting Sunday, according to the Denver Channel. About 8,000 were still without power Monday night.

Heavy snow also affected parts of Montana. The National Weather Service issued winter storm warnings and advisories for the state through Tuesday. Havre, Montana, close to the Canadian border, saw almost 15 inches of snow by Monday night. The snowfall set a record for the most the town has seen in any October: the previous record was a mere 8.6 inches in 1914. Havre’s weather technically qualifies the storm as a blizzard, the Weather Channel said.

Parts of Wyoming also saw significant snowfall. Laramie accumulated some 12 inches as of Tuesday morning, while Encampment saw more than 20 inches.

“We are kind of in a wet pattern,” said Russel Danielson, a meteorologist at the National Weather Service in Boulder, Colorado, according to the Denver Post. “So there won’t be a whole lot of melting initially. Then, toward the middle to late next week, we could see some warmer and drier conditions.”