In most of the United States, people are just starting to dig through their sheds to find their leaf rakes. But in many parts of Montana, people had to skip over the rakes and go straight for their snow shovels. Over the weekend, the northern Rockies experienced a massive late September snowstorm that dropped a whopping four feet of snow in some places.
A band of wet, heavy snow stretching from eastern Washington state to central Montana and south to Wyoming fell between September 27 and September 29, according to Weather.com. The blizzard-like conditions set records all over the map. The hardest hit area was Browning, Montana, on the Blackfeet Indian Reservation, which received four feet of snow.
Great Falls, Montana, the third largest city in the state, received 9.7 inches of snow on Saturday and another 9.6 inches on Sunday, setting new September snow records. It was also the second largest amount of snow the city has ever received in any two-day period at any time of the year.
“This has never happened, ever [in September]” Ray Greely of the National Weather Service in Great Falls tells Madeline Holcombe and Judson Jones at CNN.
Missoula, Montana, set a new September snow record with 1.7 inches, topping its 1934 record of 1.5 inches. Spokane, Washington, more than doubled its previous September snow record of 1.4 inches, which took place 1926.
East Glacier Park, a village on the edge of Glacier National Park, saw two feet of snow. It’s likely that areas higher up in the mountains received more than four feet of snow.
“You have higher terrain where you will never know how much snow fell because there is no one there to measure it,” Accuweather senior meteorologist Dan Pydynowski tells John Bacon at USA Today. “There will be areas over four feet, measured or not.”
Record cold temperatures continued through Monday night, with Great Falls hitting 12 degrees, and Browning dropping to just 2 degrees. Milder fall temperatures returned on Tuesday.
Many areas suffered power outages or downed trees from the wet snow. “With an unprecedented winter storm throwing our state a surprise in September, state and local governments are working closely together to protect the health and safety of Montanans and our top priority is making sure that happens,” Governor Steve Bullock says in a press release. “We were fortunate to receive several days of notice from the National Weather Service – which did a good job predicting the size and magnitude of this storm.”
While September snow may sound crazy to people in many other parts of the U.S., it’s actually not that rare in the northern Rockies, CNN reports. The difference this time around is the amount of snow that fell. Greely says Montana was experiencing summer-like conditions before the snows hit. The unexpected transition from summer to winter weather is likely to have impacts on crops, cattle and vegetation.
So why did such a massive early-season storm hit the Rockies? The jet stream that pushes weather from west to east across North America took a massive dip south from Canada, pulling colder air with it. A low-pressure system also moved slowly across the Pacific Northwest, bringing moist air with it. The combo of moisture and cold temperatures led to the snow. The same weather pattern has led to warmer, drier-than-usual conditions in the east and the south, where temperatures are expected to be 10 to 20 degrees above normal this week.