How hot does it get?
July highs average about 93°F. The valley has about 55 days a year at 90°F or hotter and about 9 at 100°F or hotter, with an average July low of about 62°F.
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Summer in the Treasure Valley
Heat, wildfire smoke, floating the river and burn rules
By J&H Digital Services LLCChecked Oct 23, 20267 sources
In short
Summers in the valley are hot and dry: July highs average about 93°F, with about 55 days a year at 90°F or hotter and about 9 at 100°F or hotter. Plan around heat, wildfire smoke that can arrive from late July, and canals that are cold, fast and private. State burn permits are required outside city limits from May 10 to Oct. 20, and the Boise River float season runs from late June to Labor Day.
- July
- Average high 92.7°F, low 61.9°F
- Hot days
- About 55 daysa year at 90°F or hotter; about 9 at 100°F or hotter
- Smoke season
- Usually late July to September, some years into October
- Burn permits
- Required outside city limits May 10 to Oct. 20 (free, valid 10 days)
- Float season
- Late June to Labor Day (2026 started June 20)
What is summer like in the Treasure Valley?
~55Days a year at 90°F or hotter
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1991 to 2020 average · NOAA ACIS: Boise daily data~9Days a year at 100°F or hotter
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1991 to 2020 average · NOAA ACIS: Boise daily data68Orange-or-worse air days in 2024, a heavy smoke year; 1 in 2025
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Boise metro, EPA · EPA AirData: Annual AQI by metro area (Boise City, ID)How do I stay safe and comfortable in summer?
- 1
Plan for the heat
Do outdoor activity in the morning and evening. In extreme heat, Our Path Home and Ada County post lists of indoor cooling locations, such as libraries and city halls.
- 2
Get ready for smoke before July
Buy a HEPA air cleaner and a MERV 13 furnace filter and a few N95 masks before stores sell out.
- 3
Stay out of the canals
Canals carry cold, fast water that changes constantly, and they are private property, so playing in one or along its banks counts as trespassing. Keep children and pets away.
- 4
Float the Boise River safely
The six-mile float runs from Barber Park to Ann Morrison Park, with a shuttle between them. Idaho law requires children 14 and younger to wear a life jacket, and responders advise everyone to wear one.
- 5
Know the burn rules
Outside city limits you need a free state burn permit from May 10 to Oct. 20, valid for 10 days. Campfires do not need one. Check DEQ for air-quality burn restrictions.
- 6
Water your lawn sensibly
As of October 2026 the City of Boise had no watering restrictions. It suggests watering in the cooler parts of the day, 2 to 3 times a week for 40 to 50 minutes.
Summer in the valley: common questions
When does wildfire smoke arrive?
Usually from late July to September, and some years into October. Smoke varies a lot: the Boise metro had 68 days of unhealthy-for-sensitive-groups air or worse in 2024 and 1 in 2025.
Do I need air conditioning?
With about 55 days a year at 90°F or hotter, central air conditioning or a good window unit is worth checking when you rent or buy. Ask the landlord whether it is included and who pays for repairs.
When can I float the Boise River?
The official float season runs from late June, when flows are safe, to Labor Day. In 2026 it opened on June 20. Barber Park offers free life jacket loaners and rentals, and the float is at your own risk.
Can I burn yard waste?
Inside city limits, check your city's fire department rules. Outside city limits you need a free state burn permit from May 10 to Oct. 20. Air-quality burn restrictions can also apply.
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Sources (7) · Checked Oct 23, 2026
- NOAA ACIS: Boise daily data
- EPA AirData: Annual AQI by metro area (Boise City, ID)
- City of Boise: 2026 Float the Boise season
- Idaho Department of Lands: Burn permits required May 10 to Oct. 20
- Nampa & Meridian Irrigation District: 2026 season start-up
- City of Boise: Water conservation
- KIVI: Where to find cooling spaces in Ada County (June 2026)
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