Cedar, Oak and Ragweed: North Texas Pollen and Your Air Ducts
Updated 2026-10 · Lewisville, TX
The calendar, season by season
North Texas has very little time without some pollen in the air. Allergy calendars for the area run roughly like this, with the exact weeks moving from year to year.
- Mountain cedar: late December to February, blown in from the Hill Country and the cedar country to the west
- Oak and other trees: February to June, peaking for oak from late March into early May
- Grasses, Bermuda in particular: March to September, heaviest in May and June
- Ragweed and other weeds: August to November
- Mold spores: all year, highest in the warm, humid late summer
Search interest for duct cleaning in Lewisville tracks that calendar closely. It climbs in December, runs high from March to May, peaks in April at about ten times the October figure, and falls away in the fall. April is when oak pollen is visibly coating cars on I-35E, and people look up at their registers and wonder what is in the ducts.
Where pollen actually ends up
Pollen grains are large compared with most household dust. Most of what gets inside a house comes in through doors, windows and clothes, and the share that reaches the return is caught by any reasonable filter. Very little reaches the supply ducts unless the filter is missing, does not fit its slot, or the return leaks unfiltered attic air into the system. So the ducts are rarely where a pollen problem lives. The filter and the seal around it are.
What helps in pollen season
A filter rated for the equipment, sized exactly to its slot, changed more often from February to May. Higher-rated filters catch finer particles but also restrict airflow more, and not every residential system is built for the highest ratings, so ask the company that services the system what it can take. Seal the return in the attic. Run the system fan when the house is closed up on high-pollen days. If the coil is matted, have it cleaned; a dirty coil makes a house feel stuffy whatever the pollen count.
Call for a free quote if you want someone to look at the filter setup and the return before deciding whether a cleaning is worth it.
Where to go next
Common questions
Should I book duct cleaning before or after oak season?
After, if you are booking it at all. Cleaning in March means the system pulls in the rest of the season straight after. Many companies are also less busy by June.
Will an air purifier help more than duct cleaning?
A room purifier with a proper filter can help in a bedroom. It is a different product from duct cleaning, and the whole-house version of the same idea is a good filter in the return.