October 2019 was the coldest October on record in the state of Idaho, the National Weather Service’s Boise office announced Friday.
The towns of Jerome and Fairfield had their coldest Octobers ever recorded, as did Burns, Halfway and Ontario in Oregon.
Boise saw the third-coldest October “in 80 years of airport records,” the service reported on its blog, Sage Winds. It was the sixth-coldest on record in the city itself, with only five days of temperatures above normal throughout the month. Boise experienced record cold on three days.
The cold temperatures led to one of the chilliest Halloweens in decades, although the coldest ever was in 2002, when it was just 13 degrees. The cold weather also meant that some Idaho ski areas have already started making snow, and Bogus Basin opened part of its mountain on Friday.
What causes that kind of unseasonable cold? Weather patterns that pushed in from Alaska and from the northwestern part of Canada, including from the Gulf of Alaska’s cold waters. There was not much moisture that came with them, however, contributing to a month that tied with 1965 as the 12th-driest October at the airport. There were only five days of measurable precipitation.
There were exceptions to that — a broad jet stream from the north Pacific brought “enough moisture and energy ... to produce a thunderstorm and nearly a quarter-inch of rain” on Oct. 19, according to the blog.
Winter weather visited for the first time in the last week of the month, coming down from Canada and the Arctic. That led to the first snow of the season on Oct. 29, when the airport got flurries even though it was sunny in most of Boise.
Experts say November is going to be almost the opposite. Josh Smith, a meteorologist at the National Weather Service, said temperatures were expected to be above normal for much of the month. That means more days similar to what we have experienced this week, when the weather was consistently around 50 degrees.
Predictions also call for “below-normal precipitation,” Smith said.
Boise and the surrounding areas are expected to be in the mid- or high 50s through Wednesday, with Sunday predicted to have a high temperature of 60. Lows will sit right around freezing.
There is an air stagnation advisory for the Treasure Valley and western Magic Valley until 2 p.m. Sunday. Better known as an inversion, that air stagnation can lead “to the buildup of pollutants,” the NWS advisory reads. As of Friday afternoon, the Idaho Department of Environmental Quality extended a moderate air quality advisory in place through Tuesday.