Following an unusually warm snap, temperatures in the Treasure Valley are expected to drop again

The first two weeks of January were the seventh-warmest ever recorded for this time period in Boise since the 1880s. The Treasure Valley has seen unusually mild temperatures this new year, with highs peaking into the 50s in the last three days.

Meteorologist Korri Anderson with the National Weather Service’s Boise office said the temperatures are due to a southwest flow bringing warm air from Hawaii towards the West Coast and into Idaho.

“Usually we'll get one of those storms and then it's done,” Anderson said. “But this one, they just kept coming over and over again for two weeks straight.”

The storm, called an atmospheric river, is also behind the severe floods in California. In southwest Idaho and southeast Oregon, it caused heavy rains and warmer temps, instead of the usual snowfall.

“At night, the snow will help the temperatures cool a lot colder than they would be without the snow,” Anderson added. “So like on average it’s generally about ten degrees cooler if you have a snow cover on the ground, than if you don't have one.”

Anderson said this warm spell appears to be a fluke expected to end in the next few days, with a return to chilly temperatures by Wednesday morning and a chance of one to two inches of snowfall in Boise on Wednesday night.