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July was warmest month on record for Boise

In another record, last month saw 16 total days with a low above 70 degrees, according to the National Weather Service.
Credit: Brian Myrick / Idaho Press

BOISE, Idaho — Editor's Note: This article was originally published by the Idaho Press.

July was the warmest month on record for Boise and it could have been even warmer if not for the wildfire smoke decreasing the amount of sunshine, according to the National Weather Service in Boise.

Yesterday’s high of 82 degrees ended a 45-day streak of temperatures above 90 degrees. The streak is the second-longest since a 50-day streak in 1875, according to the National Weather Service in Boise. The record-hot July follows a June that was also Boise’s hottest June on record.

“We had an average temperature of 83.8 degrees … (This July) even exceeds that crazy hot summer of 2007 … so pretty extraordinary,” National Weather Service Boise Warning Coordination Meteorologist Jay Breidenbach said. “July 2007 … it was 83.1 (degrees).”

But several other records were broken, including the longest streak of lows above 60, which currently stands at 45 days, Breidenbach said.

“That’s incredibly rare,” he said.

For 11 consecutive days between June 27 and July 7, the low temperature did not drop below 70 degrees. In another record, last month saw 16 total days with a low above 70 degrees, according to the National Weather Service Boise’s Monthly Weather Summary.

Eight people have died from heat-related causes across the state in 2021 as of noon Monday, according to the Idaho Department of Health and Welfare. Two deaths total occurred in public health districts 3 and 4, which include Ada and Canyon counties.

Three of those who died were aged 18-49 and the others were 50 or older, the department said in an email. Five deaths occurred in June and three in July. But the data is preliminary and not all deaths before Monday have been reported to the Bureau of Vital Records and Health Statistics and there are some deaths filed with a pending cause of death.

All 31 days of July hit 90 degrees and 12 days were over 100. But all 31 days above 90 only ties July 2017 and 12 days over 100 is the fourth most for the month, according to the summary.

“One piece of good news is today, if you look at climatological averages, we’re past the normal peak of summer,” Breidenbach said. “As the days get just a little bit shorter our average temperatures … start to cool off and we’ll start getting more cold fronts come through the later we get into August.”

But despite being past the normal peak of summer, Idaho is still in the middle of fire season. Fires can last into September and even October in Idaho, but the main part of fire season is July, August and into September.

The National Interagency Fire Center is predicting above normal significant wildland fire potential for the area in August and September, though fire potential should return to normal by October. 

“Typically, out west when you have record-setting temperatures, that usually comes with dry conditions. Hot and dry conditions reduce fuel moisture and when fuel moisture decreases the vegetation dries out and becomes more readily available for ignition and spread,” said Predictive Services Meteorologist Nick Nauslar, with the National Interagency Coordination Center.

In those circumstances, there can be increased and larger wildfires, he added.

The above normal outlook for wildland fires also does not bode well for smoke in the area. Many large fires are in Northern California, parts of the Northwest and the northern Rockies, so almost completely surrounding the area.

“The prevailing wind directions are really not in our favor to not have smoke,” Nauslar said. “I would say that chances of having smoke in the valley, and I’m not saying completely smoked in or anything, but having kind of a haze or smoke in the air through August into September is pretty likely.”

While temperatures will increase through the first part of the week, the National Weather Service is expecting a cold front to come through this weekend.

There’s a chance this weekend Boise temperatures could drop below 60, Breidenbach said, and on Friday smoke could blow out with the decreasing temps.

“Right now in our forecast, it looks like a beautiful day,” he said.

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