Austin's Most Brutal Allergy Season
If you've lived in Austin for more than a year, you know the feeling. Sometime between late November and February, the cedar trees in the Texas Hill Country release an almost incomprehensible amount of pollen. The sky turns orange-yellow. Your eyes water. Your sinuses feel like they've been packed with wet concrete. Welcome to cedar fever season.
Austin consistently ranks as one of the worst cities in the United States for mountain cedar (Ashe juniper) allergies. On peak days, pollen counts can exceed 20,000 grains per cubic meter, a level that affects even people who've never had allergies before.
The good news: your HVAC system, properly configured, is the most powerful tool you have for keeping cedar pollen out of your home.
Why Your HVAC Is Your Best Defense
Cedar pollen particles are relatively large, typically 20–40 microns in diameter. That's actually good news, because larger particles are easier for air filters to capture. The challenge is that Austin homes exchange air with the outside constantly through gaps, doors, and your HVAC system's fresh-air intake. Every time your system runs, it's pulling in outdoor air, and during cedar season, that air is loaded.
Your HVAC system processes all the air in your home every 1–3 hours. That means it has multiple opportunities per day to either filter out cedar pollen or recirculate it. The difference between a well-configured system and a poorly configured one is enormous.
Step 1: Upgrade to a MERV 11–13 Filter
This is the single highest-impact change you can make. Standard 1-inch fiberglass filters (MERV 1–4) capture large debris but let most pollen pass right through. A MERV 11–13 filter captures particles as small as 1–3 microns, well within the range of cedar pollen.
A few important notes for Austin homeowners:
Don't go above MERV 13 without checking with an HVAC tech. Very high MERV filters (16+) restrict airflow significantly, which can strain your system and reduce efficiency. MERV 11–13 is the sweet spot for most residential systems.
Change it more often during cedar season. A filter that normally lasts 90 days may need replacing every 30–45 days during peak pollen months (December–February). A clogged filter is worse than no filter, it restricts airflow and lets pollen bypass the edges.
Upgrade to a 4-inch media filter if your system supports it. These thicker filters have far more surface area and last longer without restricting airflow. They're one of the best upgrades for allergy sufferers.
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Step 2: Add a Whole-Home Air Purifier
Filters capture particles that pass through them, but they don't do anything about particles already circulating in your home, or microorganisms too small to be caught. That's where a whole-home air purifier like the REME HALO or iWave comes in.
These devices install directly in your ductwork and actively treat the air throughout your home, not just at the filter. The REME HALO uses a combination of UV-C light and a catalytic process to create low concentrations of hydrogen peroxide that disperse through your home, neutralizing allergens, bacteria, viruses, and mold spores on contact. The iWave uses needlepoint bipolar ionization to break down pollutants at the molecular level.
For cedar fever sufferers, the combination of a MERV 13 filter plus a whole-home air purifier is genuinely transformative. Many Austin homeowners report that their indoor allergy symptoms drop dramatically within the first week of installation.
Step 3: Run Your System on Fan Mode During Peak Pollen Hours
Cedar pollen counts are highest in the morning, typically between 5 a.m. and 10 a.m. During this window, keep windows and doors closed and run your HVAC fan continuously (set the fan to "ON" rather than "AUTO" on your thermostat). This keeps air circulating through your filter constantly, rather than only when the system is actively heating or cooling.
Note: Running the fan continuously does increase energy use slightly. A variable-speed air handler handles this much more efficiently than a single-speed unit, another reason a system upgrade can pay off for allergy sufferers.
Step 4: Seal Duct Leaks
If your ductwork runs through an unconditioned attic, which is common in Austin homes, and it has leaks, you're pulling unconditioned (and unfiltered) outdoor air directly into your living space. During cedar season, this is a significant source of indoor pollen.
A duct leakage test can identify how much air your system is losing. Sealing duct leaks typically costs $500–$1,500 and can reduce indoor allergen levels substantially while also improving efficiency.
The Bottom Line
Cedar fever is a fact of life in Austin, but suffering indoors doesn’t have to be. A MERV 11–13 filter, a whole-home air purifier, and a few smart operating habits can turn your home into a genuine refuge during the worst months of the year.
For a deeper look at which filter to pair with your system, see our MERV filter guide for Austin homeowners [blocked]. If you're also dealing with spring allergies, our spring pollen guide [blocked] covers what comes next after cedar season ends.
