Wildfire smoke in summer, inversions in winter, and how to check the air
By J&H Digital Services LLCChecked Oct 202613 sources
In short
Most days the air in the Treasure Valley is good. The two problem seasons are late summer, when smoke from wildfires across the West can drift in for days or weeks, and winter, when inversions trap cold, polluted air in the valley. Check Idaho DEQ's daily forecast or AirNow before outdoor plans, and follow burn restrictions on bad air days. In 2024, a heavy fire year, the metro had 68 days of air unhealthy for sensitive groups or worse; in 2025 it had 1.
Smoke season
Usually late July to September, some years into October
Inversion season
Usually November to February
Where to check
Idaho DEQ forecasts and map, or AirNow.gov
Burn restrictions
Wood stove and open burning limits on DEQ alert days in Ada and Canyon cities
Be ready with
HEPA air cleaner, MERV 13 furnace filter, N95 masks
What else do people ask about smoke and air quality?
How bad is wildfire smoke in Boise?
It varies a lot by year. From 2020 to 2025 the Boise metro had anywhere from 1 to 68 days a year in the orange range or worse, with 2024 the worst. Some summers have only a few hazy days; others have weeks of smoke from fires in Idaho, Oregon, California or Washington. Smoke usually arrives from late July through September. On the worst days the air can reach the red (unhealthy) range or worse for everyone, not just sensitive groups. Smoke can also make summer heat feel worse, since you may need to keep windows closed.
What is a winter inversion?
Normally air gets cooler as you go up. In an inversion, a layer of warmer air sits on top of cold air in the valley like a lid. Smoke from wood stoves, car exhaust and other pollution gets trapped under the lid and builds up for days, until a storm or wind mixes it out. The valley can be gray, cold and hazy while Bogus Basin and the mountains above are sunny and clear.
What are burn restrictions?
Idaho DEQ issues a daily air quality forecast for the Treasure Valley. When it calls an air quality alert, cities in Ada and Canyon counties restrict burning under their local ordinances. Depending on the city and the alert level, that can include wood stoves and fireplaces, open burning, yard debris and fire pits. Homes with no other source of heat are often exempt. Check DEQ's "Can I burn?" page or your fire department before you light a fire.
How do I check the air quality?
Use Idaho DEQ's air quality map and daily forecast for the Treasure Valley, or AirNow.gov, which shows the same official monitors plus nationwide fire and smoke maps. Both use the Air Quality Index (AQI). Check in the morning and again before evening plans, because smoke can change quickly.
What should I do on a smoky day?
Keep windows and doors closed, run your air conditioner on recirculate, and run a HEPA air cleaner in the room where you sleep. Use a MERV 13 or higher filter in your furnace or central air system if it can take one. Move workouts indoors or to early morning. If you have to be outside for long, a well-fitted N95 mask helps; cloth and surgical masks do not filter smoke well. People with asthma, heart or lung disease, older adults, children and pregnant people should take extra care.
Should kids play outdoor sports on smoky days?
Check the AQI before practices and games. Children breathe faster than adults and are more affected by smoke. At orange, cut back on hard or long outdoor activity, especially for kids with asthma; at red or worse, move it indoors or reschedule. Many local schools and leagues follow their own AQI rules, so ask your coach or school what theirs are.
Is summer heat a concern?
Yes. Boise averages about 55 days a year at 90°F or hotter and about nine at 100°F or more. The dry air helps nights cool off, but heat is still dangerous for kids, older adults, pets and people working outside. Plan outdoor activity for mornings, drink water, and never leave anyone in a parked car. Watch for heat exhaustion signs such as heavy sweating, dizziness, nausea and cramps, and call 911 for confusion or fainting, which can mean heat stroke.
03
How many unhealthy air days does Boise get?
Year
Orange (sensitive groups)
Red (unhealthy)
Purple (very unhealthy)
Worst AQI
2020
10
10
1
223
2021
16
4
0
173
2022
11
2
0
188
2023
3
0
0
120
2024
33
31
4
265
2025
1
0
0
135
Boise City metro area (Ada, Canyon, Boise, Gem and Owyhee counties). Most bad days are wildfire smoke in July to September; a few are winter inversions. 2025 figures may still be revised. Source: EPA AirData: Annual AQI by metro area (Boise City, ID)
04
What do the air quality colors mean?
AQI
Color
What it means
0 to 50
Green: Good
Air is fine for everyone.
51 to 100
Yellow: Moderate
Acceptable; very sensitive people may want to limit long outdoor exertion.
101 to 150
Orange: Unhealthy for sensitive groups
Kids, older adults and people with heart or lung conditions should cut back outdoor exertion.
151 to 200
Red: Unhealthy
Everyone should limit time and exertion outside.
201 to 300
Purple: Very unhealthy
Everyone should avoid long or heavy outdoor exertion.
301 and up
Maroon: Hazardous
Stay indoors with filtered air if you can.
Idaho DEQ's forecasts and burn restrictions use these same color levels. Source: AirNow (U.S. EPA)
05
How do I get ready for smoke season?
1
Buy a HEPA air cleaner
Size it for your bedroom or main living area. Buy before July; stores can sell out during smoke events.
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