‘Intense’ heat wave could break Boise’s temperature record? Cool. Here are the details

It’s about to get seriously hot in Boise.

All-time, record-breaking hot.

Run-the-hell-inside hot.

The National Weather Service in Boise forecasts temperatures to get well above 100 degrees for multiple days next week, and there’s a slight chance that Boise will equal or break its heat record.

A heat wave caused by a high-pressure system coming inland from the Pacific Ocean will bring extreme temps to much of the West starting this weekend, including the Gem State. The weather service predicts that Boise will hit 100 starting Saturday, and it forecasts a high of 106 degrees on Tuesday — before getting even hotter later in the week, meteorologist Jackson Macfarlane told the Idaho Statesman.

“Our all-time record for Boise is 111 degrees Fahrenheit for an afternoon high,” Macfarlane said. “On Wednesday the 10th and Thursday the 11th ... there’s about a 20-25% chance that we could see 111. So we might be threatening that all-time record.”

Here’s what to know about the upcoming heat wave and how long it will affect Southwest Idaho.

How hot will it get in Boise?

The National Weather Service forecasts a high of 102 to kick off the weekend, after we hit the high 90s on Friday.

Macfarlane said the heat wave is caused by a high-pressure system causing a “heat dome” over the U.S. West. Although some of the extreme heat is being pulled from the south, most of it in Idaho is coming straight down.

“The high pressure caps us in the mid-layers of the atmosphere, and that traps that warm surface-layer air near the surface,” Macfarlane said. “Because we’re in early July, our sun angles are so high, and that surface heating is so intense, all that trapped air is going to bake us, kind of like an oven works.”

It will just get hotter with each passing day after the weekend, according to the weather service. The high temperature is forecast to be 102 again Sunday, followed by 104 on Monday and 106 on Tuesday. Much of the Treasure Valley will be under a high-risk heat warning, the second-highest category.

The National Weather Service issued an excessive heat warning on Wednesday that will go into effect Saturday afternoon and remain through Wednesday afternoon. The warning notes that high temperatures will persist past its current expiration and that the heat wave’s longevity makes it particularly dangerous to people and pets outside.

Although the National Weather Service doesn’t forecast past Tuesday, Macfarlane expects the hottest period to be Wednesday through Saturday next week. Wednesday and Thursday will be the hottest days, with temperatures creeping close to that 111-degree mark.

What records could be broken?

NWS has been tracking weather data for Boise since 1875. If the temperature reaches 111, that would match the city’s record high, set on July 12, 1898, and matched on July 19, 1960.

Boise also has a chance to equal or surpass the record for consecutive days of 105 or hotter. The record is four, set in 2002.

Macfarlane said it’s likely that Boise will tie that record, with temperatures expected to be at least 105 from Wednesday to Saturday. He said we also could hit 105 on Tuesday and Sunday of next week; if either happens, Boise could break the 22-year-old record.

How long will the heat last?

Get ready to swim, float the river, flee to the mountains or sit in the AC, because the summertime heat isn’t going anywhere.

Macfarlane said the National Weather Service’s models go 10 days out before the forecast becomes more uncertain, but it’s a safe bet the heat wave will last until mid-July.

The Climate Prediction Center, an arm of the National Oceanic and Atmospheric Administration, forecasts further out yet more broadly than local National Weather Service offices. The CPC says that Idaho stands an 80%-90% chance of above-average temperatures until at least July 17. Boise’s outlook for the whole of July is a 70%-80% chance of above-average temperatures.

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