Boise to see second heat wave of the year. How high will temperatures rise?
After a string of thunderstorms and sub-freezing temperatures, another heat wave is coming to the Boise area.
“A warming and drying trend begins Thursday and continues through Friday as high pressure builds across the state,” the National Weather Service said in its most recent Idaho state forecast discussion.
“By the weekend, temperatures will rise 10 to 15 degrees above normal,” the weather service said, “with lower valleys in southern Idaho potentially reaching the upper 70s to low 80s.”
However, temperatures may gradually drop as clouds move in, the weather service said.
“A new system potentially brings a return of showers and thunderstorms, primarily to southern and central Idaho,” the weather agency said in its statewide forecast.
“Cooler and wetter” spring weather is expected to return next week, the weather service said.
Here’s what to expect — and when:
Will Boise heat wave break temperature records?
Although Boise set multiple temperature records during a heat wave in late March, the weather in Boise should be milder this time around.
High temperatures will be around 10 degrees lower than record highs reported in previous years.
Boise previously saw record highs in the low 90s for the time period of April 29 through May 4, according to Extreme Weather Watch.
May will still get off to an unseasonably hot start in Boise, where average high temperatures typically range from the mid- to high 60s this time of year, according to the temperature database.
What’s the weather forecast for Boise?
Wednesday, April 29, was expected to start off mostly cloudy before becoming sunny later in the day, according to the seven-day forecast.
High temperatures for Wednesday were predicted to be close to 69 before dropping to 43 overnight.
Sunny conditions were forecasted to remain on Thursday and throughout the rest of the week.
Temperatures are anticipated to break into the 70s on Thursday with the afternoon high reaching 72.
An overnight low on Thursday will drop close to 42 as wind speeds pick up overnight, gusts of up to 25 mph are expected.
Friday will see a high of 77 degrees and an overnight low close to 48 as clear weather stays in Boise.
Temperatures will jump into the 80s beginning Saturday, with a high forecasted to be around 82 degrees.
The overnight low Saturday will only lower to around 51 degrees.
The hottest day in the forecast will be on Sunday, May 2 as high temperatures heat up to 82 degrees and overnight lows cool down to 53.
Monday is expected to be another mostly sunny day with high temperatures near 82 and an overnight low staying at 53.
River levels are rising in Boise
April is shaping up to be the wettest April in Boise history, according to previous Idaho Statesman reporting.
The capital city has seen a total of 3.87 inches of precipitation so far this month, surpassing the previous rainfall record of 3.34 inches set in 1912.
As the weather warms, melting snow can lift local river levels even higher, with dangerous consequences.
“Flows are high and river conditions are changing quickly,” Float the Boise said on its website. “Use caution near the Boise River.”
Water speeds were moving at 1,522 cubic feet per second along the Boise River on Wednesday, April 29.
How to stay safe in the water
The city of Boise offers these water safety tips for enjoying recreational activities:
- Never swim alone and don’t leave children unattended in or near water.
- Don’t swim in canals. Learn to swim or stay out of deeper waters.
- Wear a life jacket when swimming in or paddling on the water.
- Know the water you are in, check the weather, current speeds and temperatures.
- Do not swim or boat while under the influence of alcohol.
This story was originally published April 29, 2026 at 12:33 PM.
