July heat breaks records in Boise, Treasure Valley

As the seventh month of 2024 draws to a close, southwest Idaho has plenty of triple-digit temperatures and smoky days to look back on.

Boise saw its third-warmest July on record, with an average temperature (calculated by averaging daily highs and lows) of 82.8 degrees, while the second-largest wildfire in the nation has burned almost 300,000 acres 100 miles to the northwest.

The hottest Boise has been in July was an average of 83.8 degrees in 2021 and 83.1 degrees in 2007.

“We’ve had all kinds of streaks for temperatures above 100 or 95 or 99,” National Weather Service meteorologist Dave Groenert said.

Several Boise temperature records were broken this month. The temperature reached or exceeded 99 degrees for 17 consecutive days, smashing the previous record of 12 days in 2021.

There were five consecutive days with temperatures at or above 105 degrees, surpassing 2022’s record of four, and nine non-consecutive days with temperatures at or above 105 degrees, surpassing 1898’s record of five.

Records tied include consecutive days at or above 100 at nine, and total days at or above 100 at 15.

Additionally, this July brought some of the highest concentrations of wildfire smoke that Idaho Department of Environmental Quality regional airshed coordinator Mike Toole has seen in several years.

“We were in the yellow [Moderate] pretty consistently, bumping into the orange [Unhealthy for Sensitive Groups], and then … took a nosedive right into that red [Unhealthy] category with some days in the purple [Very Unhealthy],” Toole said, referencing the US Air Quality Index (AQI). “You go back to 2015, and we had four days in the yellow, and that was it. This year’s impacts, so far, have been significantly higher in concentration than we’ve seen in July in the past 10 years.”

The last day of July and the first day of August were both predicted to be yellow on the AQI, according to the Department of Environmental Quality’s 3-Day Treasure Valley Forecast. Meanwhile, high temperatures are expected to climb above 100 again beginning Aug. 1, with this streak projected to continue through at least next Tuesday.