Lung health advice is usually written as if the air were a constant. It isn't. The demands rotate through a reasonably predictable twelve-month cycle, and seeing the shape of it explains a lot of things that otherwise feel random.
January and February
Peak indoor season. Heating runs constantly and pulls humidity down, sometimes to levels comparable with arid climates. Dry air thickens the mucus layer, and thick mucus moves poorly — which is the mechanical reason winter mornings so often begin with throat-clearing. Windows stay shut, ventilation falls, and people spend far more time indoors in company.
March, April, May
Tree pollen first, then grass. For sensitised people this is a months-long stretch, not an event, and it gets consistently misread as a cold that won't shift. The giveaway is itching — infections rarely itch. Pollen seasons have also been lengthening as growing seasons stretch, so the pattern you remember from two decades ago may not be the pattern now.
June, July, August
Ground-level ozone is the summer pollutant, formed when sunlight reacts with traffic emissions. It peaks on hot, still, sunny afternoons rather than at rush hour, which catches people out. Wildfire particulate increasingly layers on top and travels far beyond any fire.
September, October, November
Three things overlap. Damp and fallen leaves raise mould spore counts, ragweed peaks across much of the country, and the heating comes on for the first time — driving a summer's worth of settled dust through the ducts in one evening. That last one is why so many people develop a cough the first cold week and assume they caught something.
What to change, and when
- Before first heating: replace HVAC filters. Doing it after the dust has already circulated is closing the gate late.
- Spring: shower and change after long spells outdoors, keep bedroom windows shut at peak counts, dry laundry indoors.
- Summer: shift hard exercise to mornings on high-ozone days. Exertion multiplies your ventilation rate several-fold, so the same hour delivers far more of whatever is out there.
- Winter: a hygrometer and a humidifier, aiming for 30 to 50 percent.
None of this requires buying much. Most of it is timing.
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