Montana Gov. Steve Bullock declared an emergency Sunday as a rare September snowstorm walloped the Northern Rockies with powerful winds and as much as 3 feet of snow.

Calling the storm “unprecedented,” Bullock said that strong winds downed power lines shutting down roads, triggering outages and hampering cellphone service.

"In terms of how widespread and strong this storm has been, we still have a lot of data crunching to do, but it appears that this storm could end up being one of, if not the strongest on record" for early fall, Matthew Jackson, a National Weather Service senior meteorologist, said.

Jackson said a three-day period in September 1934 was the last time so much snow fell in such a short amount of time.

But that record — 13.2 inches in the city of Great Falls — had already been eclipsed by this weekend's snowy weather, when almost 19 inches fell in just two days.

"As we are still snowing, that number will likely increase tonight," he said.

People walk along a snow covered street in Helena on Sunday. Matt Volz / AP

Bullock's emergency declaration targeted eight counties in western Montana, as well as the Blackfeet Indian Reservation, allowing state officials to more easily help hard-hit areas.

There were no immediate reports of injuries or deaths. No major interstates were affected, though the state Department of Transportation said that snow and ice had closed several smaller roads.

The storm mostly spared the state's largest cities, Billings and Missoula. But Great Falls, population 58,000, saw a record 14 inches fall overnight Saturday, NBC affiliate KECI reported.

On Sunday afternoon, forecasters with the NWS said that some areas of western Montana could see another 1 to 2 feet of snow overnight.

In the Blackfeet town of Browning, the local emergency operation center reported 40 inches of snow by Sunday morning, according to the Weather Channel.

NBC affiliate KECI reported that public schools, community colleges, tribal offices and medical facilities in the town would remain shuttered Monday.

Much of Glacier National Park was closed because of the storm, but that didn't stop out-of-state visitors from seeking free access Saturday on National Public Lands Day, the station reported.

"We packed our winter gear and were determined to not let it stop us from going on a hike today,” Amanda Peacock, of Chicago, told the station.

The storm also brought record-setting snowfall to Spokane, Washington, where almost 2 inches of snow fell Saturday night, NBC affiliate KHQ reported.

The previous record of 1.4 inches was recorded in 1926 — for the entire month of September, the station reported.

Another inch of snow had already fallen by Sunday morning, according to KHQ.