A heat wave is on the way to Idaho, setting up a toasty June. Here’s how hot it will be
Meteorological summer began over the weekend as the calendar ticked to June, and right on cue, the weather in Boise is expected to turn very summer-like.
A heat wave originating from Mexico will move northward later this week, pushing temperatures in Boise into the 90s for several days.
But first, there’s one last day of spring weather to get through. Here’s what to know about this week’s forecast.
A final day of spring weather
Many Idaho residents became accustomed to the term “atmospheric river” last winter, as numerous large swaths of water vapor from the Pacific Ocean blasted the Gem State.
An atmospheric river, often nicknamed the “Pineapple Express” by meteorologists, is an extended, narrow region in the atmosphere that transports large amounts of water vapor from the area around Hawaii to the West Coast, according to the National Oceanic and Atmospheric Administration.
They typically occur in the winter months, but a late-season atmospheric river moved into the Pacific Northwest over the weekend and was lingering through Monday.
As of 6:30 a.m. Monday, 0.21 inches of rain fell at the Boise Airport, and between 0.35 and 0.6 inches at higher elevations, National Weather Service meteorologist Sophia Adams told the Idaho Statesman.
Weather Service meteorologist Jackson Macfarlane said that although Boise was looking at a 90% chance of rain for the remainder of Monday, it was primarily going to be spottier showers in the Treasure Valley.
The heavier rain was expected to remain in the mountains north of Boise, where a flood watch was issued as the rain combined with snowmelt to threaten low-lying and flood-prone areas.
“Later (Monday) afternoon, we are expecting a few heavier showers (in the mountains), possibly a thunderstorm or two to get going,” Macfarlane told the Statesman. “And the rainfall rates out of those could be heavy to moderate on already saturated soils from overnight. So that’s where the highest flash flood potential exists.”
A heat wave to kick off summer
Summer will arrive with a bang later this week as a high-pressure system from Mexico moves northward through the Great Basin.
Parts of Mexico hit 115 degrees over the weekend, and as the high-pressure system shifts northward, similar temperatures will follow. The Weather Service forecasts that Boise will reach 96 degrees by Saturday — the hottest temperature in the current forecast — but the heat will arrive before then.
On Monday, the Weather Service was forecasting a high of 80 degrees for Tuesday, 84 for Wednesday, 92 for Thursday and 94 for Friday.
Although some meteorologists were describing the high-pressure system as a “heat dome” — a similar phenomenon caused record-breaking heat in Boise last year — Macfarlane said this event would be better described as a heat wave for Boise.
“If the center of the high pressure was directly over us, I might be more willing to call it a heat dome,” Macfarlane said. “But because we are north of the center, and we’re kind of in the ridging portion of that high pressure, I think it’s just better to call it a heat wave.”
Even once the heat wave passes, Macfarlane expects temperatures to remain warm in Boise moving forward in June.
The Climate Prediction Center, an arm of NOAA, forecasts that most of Idaho will experience a 50-60% chance of higher-than-average temperatures in June. Historically, Boise sees the average high rise from 76 degrees in early June to 87 by the end of the month.
This story was originally published June 3, 2024 at 12:42 PM.
