No, you weren’t imagining it. Boise really did have unusual weather this summer
In 1864, the Idaho Territorial Legislature voted to make Boise the state capital, the Idaho Statesman published its first edition and officials at Fort Boise began keeping local weather records.
In the 160 years since then, 2024 was the second-hottest summer recorded in Boise, according to the National Weather Service. Only 2021 saw a more sweltering summer here.
Weather experts wanting to calculate how unusual a summer was can compare temperatures to the overall average temperature for Boise summers between 1991 and 2020, which was 73.63 degrees.
Idaho’s average temperature this summer was 77.4 degrees, coming close to 2021’s summer record of a 78-degree average, according to Sophia Adams, a National Weather Service meteorologist in Boise.
June’s average temperature was 4.4 degrees above the overall average, July’s was 5.2 above and August’s was 1.7 above, Adams said.
2024 saw 20 days over 100 degrees, which didn’t quite break 2022’s record of 23 days of 100-plus weather, according to the National Weather Service. When it comes to lows, 2024 tied the 2021 record of 21 days with a low temperature above 70 degrees.
A weather transition period is likely part of the reason for the extreme heat. The climate is in the process of shifting between two different oceanic weather cycles, going from an El Nino summer to a La Nina winter, according to Adams.
“Typically, during those transition times, we can see extreme heat or extreme cold,” Adams said by phone.
This year, Adams said, the transition brought with it a prolonged period with an extensive upper-level high-pressure system that stayed over the western United States for weeks at a time.
That type of high-pressure system is typical for the Rocky Mountains region, but usually lasts only a few weeks before moving on, allowing the temperature to lower.
That system is still affecting the weather, making for a hot September in Idaho so far.
Boise’s low of 71 degrees on Sunday was the warmest low temperature recorded so late in the year, beating out previous records set in 2014 and 2017, according to the National Weather Service.
But Boise wasn’t alone in trying to beat the heat over the past three months. The European Union’s Copernicus Climate Change Service found 2024 was the hottest summer recorded on Earth since the 1850 pre-industrial period.
“During the past three months of 2024, the globe has experienced the hottest June and August, the hottest day on record, and the hottest boreal summer on record,” Samantha Burgess, deputy director of the Copernicus Climate Change Service, said in the organization’s recent report. “This string of record temperatures is increasing the likelihood of 2024 being the hottest year on record.”
One of the most obvious consequences of this extra heat in Idaho is the increased risk of wildfires.
“The lack of precipitation and those extremely hot, hot temperatures leading to much drier conditions and lower relative humidities across the region has led to this fire season being pretty extreme,” Adams said.
More than 389,00 acres have burned in Idaho so far this year, according to the Department of Lands.
Cooler days on the horizon
But there’s hope yet for those craving cool, autumn days. The National Weather Service said an upper-level low-pressure system from the Pacific Ocean is headed for Boise.
“It’s a pretty significant pattern shift, which will be a welcome relief, especially after some of those hotter temperatures across the region,” Adams said.
Adams predicted the cold front would begin moving in Wednesday, ushering in rain and scattered thunderstorms either in the afternoon or overnight into Thursday. Temperatures are expected to drop to 76 degrees on Wednesday and the upper 60s on Thursday.
“That could give us at least a quarter of an inch of rain in the Boise area and maybe higher amounts in the mountains,” Adams said.
