Bundle up, trick-or-treaters. An unusually wet, cold October in the Black Hills is ending with a brisk Halloween night.

Today’s temperatures will reach the mid- to upper-40s in Rapid City, with little wind and some clouds but no precipitation in the evening, according to Steve Trimarchi, a meteorologist with the National Weather Service in Rapid City. Throughout the Black Hills, temperatures will likely be in the 30s, dropping to the 20s in the evening.

“Halloween will be kind of chilly but not too bad compared to what it’s been for the last few days,” Trimarchi said.

Rapid City experienced its sixth snowiest October on record since 1888, Trimarchi said. Although nowhere near the record snowfall of Winter Storm Atlas in 2013, Rapid City received between 6 and 12 inches of snow throughout the city this month. The average snowfall for October is 2.5 inches.

In the Southern Hills, Hot Springs typically gets an inch of snow in October, but 8.7 inches fell this month. Snow amounts vary throughout the Northern Hills, but Lead experienced its seventh snowiest October with 38 inches. The average October snowfall there is 18 inches, Trimarchi said.

“It’s definitely unusual to have that amount in October,” Trimarchi said. “I don’t think we’ll get anything else through (Halloween) night.”

The snow has been accompanied by some record low temperatures. On Oct. 30, the temperature at Rapid City Regional Airport dropped to -2, tying a record low in 1991, Trimarchi said. Mount Rushmore reached record low temperatures of 4 degrees on Oct. 29 and 11 degrees on Oct. 27. Temperatures dropped below zero in the Black Hills recently, but did not hit record-breaking lows, he said.

October’s cold and snow is caused by a pattern of cold air from Canada that’s affected western South Dakota for about two years and especially since February, Trimarchi said.

“We’ve stayed in a fairly persistent pattern of near- to below-average temperatures and with it being wet, that keeps it cold,” he said. “This cold snap of clipper systems coming through that have brought Canadian air have been quite chilly.”

The Black Hills can expect warmer temperatures, then cold with snow, to continue for the next week or two and possibly longer into November, Trimarchi said.

“It’ll try to warm a little bit and it will cool down again. It’s a yo-yo pattern. … It doesn’t look like it will be as cold as it has been in the mornings at least for the next few days to a week,” he said, adding that temperatures will likely still be cooler than average.

“As we get into winter, it could be a lot like later last winter and spring. I would expect this general pattern of colder than average and wetter than average, especially for the Northern Hills, for a while,” he said.

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