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Why are there fire ant mounds in my Brownsville yard after the rain?
Heavy rain can push colonies up to the surface and send them looking for dry ground, including your foundation, patio, A/C pad and the inside of your home. After flooding, AgriLife says colonies move to dry ground and debris until they re-establish in the soil (Texas A&M AgriLife, Flooding and Fire Ants). If you’re seeing mounds or ants indoors, CPL Pest Control LLC can inspect your Brownsville property, find where the colonies are, and treat them.
Fire ants in your Brownsville yard, driveway or house? Call or text Chris at (956) 287-2118 for a free inspection. Our Rio Grande Valley line answers 24/7.
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Don’t step on, kick or dig into the mounds, and keep kids and pets away until they’re treated.
What happens to fire ants when the ground floods?
Texas A&M AgriLife entomologist Robert Puckett says fire ants forage when temperatures are about 70°F or higher (AgriLife Today, March 10, 2026). They don’t drown, they float. Texas A&M AgriLife says floodwater will not drown fire ants. Instead, the colony leaves the soil, forms a loose ball or ribbon, and floats until it reaches dry ground or something it can climb (Texas A&M AgriLife, Flooding and Fire Ants). AgriLife entomologists warn that ants in a floating mat are more aggressive and can swarm anything they touch (AgriLife Today, Aug. 30, 2017).
As the water drops, AgriLife says, those colonies can end up in debris piles and in homes and other buildings until they build new mounds in the soil. So after rain you may find fire ants:
- On top of or under piles of yard debris, firewood and stored items
- Along the foundation, slab edges, patios and steps
- Around A/C pads, electrical boxes and meters
- Under carpet edges, furniture or stored boxes in a garage or ground-floor room that took on water
What makes Brownsville a fire ant hot spot after rain?
Brownsville has several things working together:
- Resacas wind through town. Resacas are former channels of the Rio Grande. The National Park Service says they stay dry in their natural state, fill during heavy rainfall, and the larger ones can hold water for days or weeks afterward (National Park Service, Resaca Overlook). Brownsville is estimated to have about 3,500 acres of resacas (Brownsville Public Utilities Board, Resaca Natural Resources Appendix). Yards backing up to a resaca or drainage ditch stay wet longer.
- It floods in a hurry. On March 26 to 28, 2025, Brownsville recorded 6.74 inches of rain, the wettest March three-day total at its station, which has records back to 1878, and the Rio Grande Valley saw a disaster declaration for all four counties (National Weather Service Brownsville, Historic Flooding of March 26-28, 2025).
- Cameron County is fire ant country by regulation. The Texas Department of Agriculture lists Cameron County among the counties under the imported fire ant quarantine (Texas Department of Agriculture, Red Imported Fire Ant). The quarantine is about moving soil, sod and plants out of infested areas, so the state treats the county as infested.
How can I tell fire ant mounds from other mounds?
Fire ant mounds are loose, dome-shaped piles of soil, and they usually have no single obvious entrance hole. The ants come pouring out fast when you disturb one, and they sting repeatedly. Stings can leave itchy white pustules, and some people have serious allergic reactions. AgriLife’s flood guidance says to seek immediate medical care for signs such as trouble breathing, severe swelling or nausea after stings (Texas A&M AgriLife, Flooding and Fire Ants). This is general information, not medical advice.
Mounds against slabs, siding and trees are common spots to look.
Free inspection. Not sure what’s in your yard? Chris will walk your property, show you where the mounds and nests are, and tell you what he recommends before any work starts. Book your free inspection or call or text (956) 287-2118.
Should I treat fire ants right after a flood?
Not with bait, according to AgriLife. Texas A&M says fire ant baits shouldn’t be used right after a flood, because they work slowly, the flooded colonies are disorganized, and the workers aren’t foraging for food (Texas A&M AgriLife, Flooding and Fire Ants). That’s one reason timing matters, and one reason to have a pro look before you spend money on products that won’t work yet.
When you handle debris after rain, AgriLife recommends:
- Wear cuffed gloves, rain gear and rubber boots (AgriLife flood guide).
- Use a shovel or other tool instead of your hands.
- Remember fire ants can be under or inside anything that has sat wet for a few days, including old wood, boxes and carpet edges.
What does CPL do for fire ants in Brownsville?
When you call CPL Pest Control LLC, here’s how it works:
- Inspection. We walk the yard, foundation and any rooms where ants are coming in, and find the mounds and the places the ants are traveling.
- Treatment. We treat the fire ants we find in the yard, along the foundation and where they’ve gotten into the house.
- Fixing the cause. We show you what’s attracting them, such as wet low spots, debris against the house and gaps along the slab, so you know what to change.
Fire ants aren’t the only pest that wet weather brings indoors. CPL Pest Control LLC also handles roaches, rodents, scorpions and other pests that come in with wet weather. See pest control in Brownsville for the full list.
Frequently asked questions about fire ants in Brownsville
Why do fire ants come into the house when it rains?
Flooded or saturated colonies look for dry ground. AgriLife says floating colonies can end up in homes and other buildings until they build new mounds.
Can fire ants float on floodwater?
Yes. AgriLife says colonies form a ball or ribbon and float until they reach dry ground. Avoid touching them.
Should I use fire ant bait right after heavy rain?
AgriLife says no. Baits are slow and flooded colonies aren’t foraging, so they won’t work yet.
Do fire ants stay active in Brownsville in winter?
They forage when it’s about 70°F or warmer. Brownsville often has fall and winter afternoons above 70°F.
Is the inspection free?
Yes. The inspection is free, and you’ll get a price before any work starts.
Do you answer after hours?
Yes. Our Rio Grande Valley line answers 24/7 at (956) 287-2118.
¿Hablan español?
Sí. Llame o envíe un mensaje de texto a Chris al (956) 287-2118. También puede leer nuestra página de control de plagas en Brownsville.
Ready to deal with the fire ants at your Brownsville home?
Call or text us, tell us where you’re seeing mounds or ants, and we’ll come out and find them. Our guarantee: Full 30 day money back guarantee, if you are not completely happy with our service.
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Related reading and services:
- Pest control in Brownsville, TX
- Control de plagas en Brownsville, TX
- Mosquito control in Brownsville
- Pest control in the Rio Grande Valley
- Contact CPL Pest Control
About the author: Christopher Villarreal owns CPL Pest Control LLC (Texas TPCL license 0567655) and has over 20 years of experience in pest control. CPL Pest Control LLC is fully licensed and insured and serves Brownsville, McAllen, Edinburg and the Rio Grande Valley.
Published November 9, 2026.
