Cedar Fever in Norman: Why January Is the Worst Month for Indoor Air

Oklahoma's allergy calendar does not start in spring. It starts in January, when mountain cedar pollen drifts north out of central Texas, and it is reinforced through late February by our own eastern red cedar. The Oklahoma Allergy & Asthma Clinic tracks tree pollen beginning as early as January, well before anything looks like it is blooming.

That timing matters in Norman because it collides with heating season. Your furnace or heat pump is running long cycles, the house is shut up tight, and every cycle pulls air through whatever filter is in the return. Cedar pollen is small and it gets everywhere. A standard one-inch fiberglass filter is designed to protect the equipment, not your sinuses — it will pass a great deal of what is bothering you straight back into the house.

Norman's pre-war housing around the Chautauqua district and Campus Corner is the hardest hit. Tight crawl spaces, ductwork that was retrofitted into a house never designed for it, and returns cut to whatever size would fit between the joists rather than what the blower actually needs.

Two things help more than anything else. First, a genuinely better filter — a pleated media filter in the MERV 11 to 13 range captures far more pollen than the cheap flat ones, though it has to be matched to your blower or you will choke airflow and drive up static pressure. Second, change it on a schedule during January and February rather than when you remember. A loaded filter is a bad filter.

If someone in the house reacts hard every winter and you have never had the ductwork looked at, that is worth a visit. Leaky return ducts running through an attic or crawl space pull in unfiltered air from exactly the places you do not want it coming from.