Cedar fever hits the Hill Country from December through February, when Ashe juniper releases pollen in quantities that turn car hoods yellow and close school gyms. Most people think of it as an allergy problem. It is also a pest problem. The same cracks and gaps that let pollen drift into your home are the ones scorpions, rodents, and cockroaches use when outdoor temperatures drop. Winter in this region does not kill pest populations — it moves them inside.
Quick answer
Hill Country winters are mild enough that many pests remain active or seek shelter indoors during cedar fever season (December through February). Rodents, scorpions, cockroaches, and spiders are the primary winter concerns, often entering homes through the same cracks that allow cedar pollen to drift in.
Dealing with this right now?
Winter pest pressure in the Hill Country is real and often underestimated. A seasonal inspection before or during cedar fever season can identify entry points, detect early rodent activity, and protect your home through the coldest months. Contact ACI Pest to schedule a winter inspection.
See how we handle it on our pest control page.
Why Hill Country Winters Do Not Stop Pest Activity
The Edwards Plateau rarely experiences prolonged hard freezes. Average January lows in the Marble Falls and Kingsland area stay in the mid-30s Fahrenheit, which is cold enough to slow many insects but not cold enough to kill overwintering populations or prevent active species from moving indoors. This is fundamentally different from pest dynamics in colder northern climates, where a genuine killing frost can collapse many pest populations for months.
Cedar fever season also correlates with elevated cedar bark beetle activity on stressed or dead juniper trees, which can draw woodpeckers that expose cavities later used by rodents. The pollen itself is not a pest issue, but the behavioral changes in humans — opening windows less frequently, running HVAC systems in recirculation mode — reduce the ventilation that helps detect musty odors associated with rodent harborage inside wall voids.
Scorpions in Winter: The Indoor Shelter Pattern
Bark scorpions (Centruroides sculpturatus) do not hibernate. In the Hill Country's mild winters, they remain active and move toward heat — which means toward occupied structures. Bark scorpions are capable climbers and will ascend exterior stone walls to reach attic vents, weep holes, and gaps around cable penetrations. They are most commonly found in winter inside closets, under bathroom vanities, in shoe racks near exterior doors, and in garage ceiling tracks.
The single most effective winter scorpion prevention step is sealing the exterior shell of the structure: weather stripping on doors, foam backer rod in expansion joints around the slab, and steel wool or copper mesh in weep holes. A UV flashlight inspection inside the home at night is useful for detecting scorpion activity before it becomes apparent through a sting.
- Seal weep holes with stainless steel mesh inserts, not solid material that blocks drainage
- Replace worn door sweeps on all exterior doors, including the garage entry door
- Inspect the attic for gaps around ridge vents and gable vents
- Shake out shoes stored near exterior doors before wearing
- Keep bed linens from touching the floor in bedrooms
Rodents: The Primary Winter Pest Concern
House mice and roof rats begin entering structures in the Hill Country as temperatures drop in October and November, and populations already inside walls intensify their activity through cedar fever season when outdoor food sources are reduced. Rats in particular exploit the oak canopy common in Marble Falls neighborhoods, using tree limbs that overhang rooflines to access the structure from above.
Signs of winter rodent activity include gnaw marks on food packaging, droppings in the back of kitchen drawers or along wall edges, grease trails on baseboards, and scratching noises in ceilings or walls after dark. A single mouse can squeeze through a gap the diameter of a dime; rats require only a quarter-sized opening. Inspection of the roofline, soffit vents, and utility penetrations on the exterior is the starting point for any winter rodent exclusion program.
Overwintering Insects: Boxelder Bugs, Stink Bugs, and Lady Beetles
The Hill Country sees periodic mass aggregations of boxelder bugs and brown marmorated stink bugs on south-facing walls during late fall as these insects seek thermal mass before the cold sets in. While neither species reproduces indoors or causes structural damage, large numbers can be distressing and their odor — particularly from stink bugs when disturbed — is objectionable.
Asian lady beetles (often mistaken for ladybugs) aggregate in attics and wall voids in the same pattern. These overwintering insects are best managed at the point of entry in fall rather than trying to vacuum or treat them once they are already inside. Exclusion of south- and west-facing wall openings before the first cold front in October is more effective than any chemical approach once masses have entered.
Maintaining Pest Protection Through Cedar Season
Homeowners with quarterly pest service plans sometimes question whether their winter visit is necessary given the assumption that cold weather controls pest populations. In the Hill Country context, the winter visit is often the most important one for interior pest pressure because it addresses rodent harborage, overwintering spiders and scorpions, and the cockroaches that have moved deeper into wall voids to escape cooling exterior temperatures.
Cedar fever season is also a practical reminder to inspect the exterior of your home for gaps and cracks that developed over the summer — thermal expansion and contraction in limestone and mortar creates new entry points each year. Catching these openings before they are exploited by overwintering pests is far easier than treating an established infestation in February.