Boise to see second heat wave of the spring. 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.
“Cooler and wetter” spring weather is expected to return next week, according to the NWS.
But in the meantime, 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 should be milder this time around.
High temperatures will be around 10 degrees lower than records reported in previous years. Boise has seen record highs in the low 90s for the period of April 29 through May 4, according to Extreme Weather Watch. It will be in the 80s this weekend, the weather service said, but not the 90s.
That means May still will get off to an unseasonably hot start in Boise, where average highs range from the mid- to high 60s this time of year, according to the temperature database.
What’s the weather forecast for Boise?
Wednesday started off mostly cloudy before becoming sunny later in the day, with the high temperature expected to be 69 degrees, with the low dropping to 43 overnight.
Sunny conditions continue on Thursday, April 30, and through the rest of the week. On Thursday the high will reach 72, while the overnight low will be 42. Wind speeds pick up overnight, with gusts of up to 25 mph expected. Friday, the first day of May, will see a high of 77 and an overnight low of 48.
Temperatures then will jump into the 80s over the weekend, with highs of 82 on Saturday.
The hottest day of the week is Sunday, with highs peaking around 83. The lows over the weekend will be in the low 50s, the weather service said.
Monday is also expected to be mostly sunny, with a high temperature near 82 and an overnight low of 53.
River levels are rising in Boise
April is shaping up to be the wettest 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 from the mountains 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. The annual summer river floating season is still a couple of months away.
How to stay safe in the water
The city of Boise offers these water safety tips for enjoying recreational activities, once the weather warms and the Boise River is safe for all recreational use:
- 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.
