The dust is back by Tuesday

You dusted the shelf on Sunday. By Tuesday afternoon there’s a fine gray film on it again, and the window was closed the whole time. Blame Denver. Dry air and a dusty, windy climate put that film on shelves across the city.

Denver’s normal annual precipitation is 14.48 inches, on the 1991 to 2020 averages the National Weather Service uses (NWS Denver/Boulder, annual climate report). 2025 came in a little wetter, at 15.42 inches. The year’s average wind speed was 9.9 mph. One July gust hit 70 mph.

Wind off the mountains, and not much rain to wash it out of the air.

The Colorado Climate Center at Colorado State University describes the plains climate this way: low relative humidity, abundant sunshine, infrequent rain and snow, moderate to high wind. Winter brings dry air and strong winds, and the Chinooks that pour down the Front Range arrive warm and fast (Colorado Climate Center).

For a home, that comes to 3 things. Dust arrives on the wind, and little rain washes it out of the air. The air indoors is dry most of the year. And whatever you open a window for comes in with the breeze.

Dry air gives and takes

Here’s the good news, the kind you only get in a dry city.

Dust mites like humidity above 50%, according to the Asthma and Allergy Foundation of America. They like it warm too, around 70°F and up. Mold needs moisture and a day or 2. Both are easier to hold off here than in a humid city. The CDC’s target of 30% to 50% indoor humidity is one a Denver home meets more easily than most, especially once the furnace is running (CDC, controlling asthma triggers). Mites still live in any bedding, so the weekly hot wash still applies. But the odds are on your side.

Dry air has a catch of its own. Levi Keller, an allergist at the University of Colorado School of Medicine, notes that in a dry climate like Colorado’s, nasal dryness can add to congestion. He also notes that windy days blow pollen into the air and spread it over a wider area (CU Anschutz). Dust travels the same way, on the wind, and with little rain to wash it out it keeps arriving. Hence the shelf.

Pollen runs most of the year

Keller lays out the Colorado calendar. Trees start releasing pollen in late winter and early spring. Grasses follow and cause symptoms through most of the summer, typically April to July. Ragweed and other weeds take over into the fall, until a freeze shuts them down. That’s 8 or 9 months when an open window is an invitation.

A closed window on a windy day keeps the day’s pollen off the couch.

His advice overlaps with cleaning almost line for line. Keep windows closed during pollen season, shower or change clothes after time outdoors, and wipe the dog down with a damp towel at the door. Each one keeps the day’s pollen off the surfaces you sleep and sit on.

The Front Range routine

Put the climate and the agencies’ advice together and a Denver week looks like this.

  • Dust damp, every week. In dry air a dry cloth throws dust into the air, and you breathe it on the way past. The allergy foundation says use a cloth that is damp or treated for dusting (AAFA).
  • Vacuum with a HEPA filter, every week. Floors, rugs, the sofa, under the bed. The filter keeps the fine, dry dust from blowing back out the other end.
  • Mat at the door, shoes off. Grit and dust walk in on feet. A mat and a shoe rack stop most of it at the threshold.
  • Windows shut on windy and high-pollen days. Air the house out when the pollen index in the forecast is low.
  • Wash bedding hot, weekly. 130°F or hotter, dried hot. Dry air slows mites down. It doesn’t get rid of them.
  • Watch humidity both ways. A meter is cheap. Under 50% keeps mites and mold down. If the winter air drops far below 30% and you run a humidifier, keep the humidifier clean and stay under the same ceiling.
  • Wipe the dog. A damp towel at the door, per Keller, before the pollen reaches the couch.
Damp cloth, every week. In this climate a dry one just moves the problem.

Twice a year, go deeper. Before the heating season, wipe the vents, vent covers and baseboards so the first warm air of October doesn’t carry a summer of dust around the house. After the weeds freeze out, do it again. That seasonal pass is the weekly list plus the edges of every room: baseboards, door frames, vents and vent covers, and the furnace filter if it’s due. How often should you deep clean? has the full seasonal list. As for the shelf, dust it damp tonight and check it on Tuesday. It’ll be better. It won’t be perfect. That’s the deal with living here.