Boise skyline smoke (copy)

It’s been a hot and hazy summer in Boise and throughout the Treasure Valley this year.

BOISE — This summer was Boise’s hottest on record, but it will likely be cooler than coming years as the West continues to become warmer and more arid.

Boise’s average temperature between June and August was 78 degrees, 1.4 degrees warmer than 2015, the former record year.

The City of Trees had 18 days with temperatures reaching 100 degrees — that’s two shy of the 20-day record from 2003.

There were nine days in a row with 100-degree temperatures, tying highs from 2015, 2006 and 2003.

Eleven days in a row with lows at 70 degrees or higher shattered the previous record of five days, set in 2015.

This year hasn’t been just hot but dry, as well, which contributed to higher temperatures, according to Joel Tannenholz, a meteorologist with the National Weather Service in Boise. The National Weather Service on Wednesday tweeted the statistics from this summer.

“Quite often when you have a drought or dry conditions, drier than normal, it will cause more extreme temperatures, especially high temperatures,” Tannenholz said.

Nine of Boise’s top 10 hottest summers have been in the 21st century. While the other averages from those years vary by 0.1 to 0.6 degrees, this year’s 1.4-degree leap past the previous record is “unusual,” Tannenholz said.

“You look at the records just about as far back as you want to go and increases have been very minor until this summer,” he said.

Boise was far from the only city to break heat records this summer. Spokane, Wash., had its hottest summer on record, as did 114 other U.S. cities, according to a report by Climate Central, a nonprofit that studies climate change effects.

Hot weather “has a lot of different impacts, from agriculture to wildfire to human health, you name it,” said Mojtaba Sadegh, Ph.D., an assistant professor in Boise State University’s civil engineering department.

The heat forced farmers to use more water, depleting reserves, Sadegh said. And it increased fuel for wildfires.

California, Oregon and Washington took the brunt of fire season, but Idahoans still dealt with the smoke. Here, 170,000 acres burned, making for a tamer season than was expected, thanks in part to a summer monsoon that brought moisture to the region, Sadegh said.

“This year we’re lucky, but we cannot really rely on luck,” he said. “One way or another, fires happening in California, Oregon are going to happen in Idaho.”

Warm weather also affects wildlife. Across the West, a compounded effect of low water levels and hot weather warmed lakes, rivers and streams, Sadegh said. Warmer water may not be suitable for cold water fish, such as trout and salmon — the pride of Idaho’s famed fisheries. In the future, that could spell trouble for not only the fish but also Idaho’s fishing communities which rely on tourist anglers.

“That warming is super dangerous for us for many different reasons, especially culturally,” Sadegh said.

The warming isn’t expected to slow. One estimate suggests the Boise area could warm by 1.8 to 5.7 degrees Celsius by the next century. That’s on top of 1.3 degrees of warming since the 19th century.

“What we had this year is basically one of the coldest summers that we’ll have in our lifetime,” Sadegh said.

Ryan Suppe is the Boise City Hall and Treasure Valley business reporter for the Idaho Press. Contact him at 208-344-2055 (ext. 3038). Follow him on Twitter @salsuppe.

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