Wildfire smoke and your windows
Smoke leaves ash and soot on glass and screens. How to clean it off without scratching the glass or breathing it in, and when to wait.
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The best time of year to wash windows in Bozeman
Late spring and early fall, for reasons you can read off a calendar: freezing nights, cottonwood season, and smoke.
Spring: after the thaw, after the fluff
Outside work needs nights above freezing, and Bozeman’s average April low is still about 30°F. By late spring that has passed, but the cottonwoods start shedding: Montana Fish, Wildlife & Parks puts their “cotton” from late May through late June. It sticks to screens and damp glass. If you can wait until it is done, the clean lasts longer.
Summer: smoke
Montana’s air quality agency notes that wildfire smoke affects the state in some summers. A smoky August leaves a film on glass, which is one more reason the fall clean is worth having.
Fall: before the freeze
September and early October are the sweet spot: the dust of summer is on the glass, the leaves are coming down, and the days are still mild. It closes quickly. The average October low at the Montana State University weather station is right around freezing, and November’s is 22°F.
| Bozeman | Average low |
|---|---|
| April | About 30°F |
| October | About 32°F |
| November | About 22°F |
| December | About 15°F |
And winter?
Inside work carries on. Outside, it comes down to the day. Can windows be washed in a Montana winter?
Whatever the season, book early. Everyone wants their windows done in the same few weeks.
Sources
- U.S. Climate Normals 1991–2020, Bozeman Montana State University station — NOAA National Centers for Environmental Information, 2021
- Black cottonwood (Montana Outdoors) — Montana Fish, Wildlife & Parks, 2020
- Air quality — Montana Department of Environmental Quality
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Read next
Winter light in Bozeman, and what your windows do with it
On the shortest day Bozeman gets under nine hours of daylight, and the noon sun barely clears 21 degrees. Why the low light favors south windows, and what clean glass can and cannot do.
Can windows be washed in a Montana winter?
Inside, yes, all year. Outside, it depends on the thermometer and on whether water will freeze on the glass.
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