Termite Swarm Season in Fresno, CA
What a swarm really is
Termite swarm season in Fresno comes in two waves. The first hits in late October, after the first real rain. The second comes at the tail end of summer, when afternoons sit in the triple digits with no wind. Both waves are swarms. A swarm is a mature colony sending out its winged breeders. Those flyers are called swarmers, or alates. Their job is to pair off and start new colonies. It’s the only time in a termite’s life that it flies. It’s also the only time most people ever see one.
Here’s the key fact. A swarm is not termites arriving. It’s termites leaving. A colony won’t swarm until it’s several years old and well established. So a swarm coming out of your house means the colony has been in it for years already. Even a swarm in the yard means a working colony within a short flight. It could be in a fence line, a neighbor’s garage, or your own walls. That’s why swarmers rank near the top of the signs worth acting on. The swarm itself is loud, brief, and harmless. The colony that sent it is the quiet, permanent thing worth finding.
The Fresno swarm calendar
- 1
First fall rains (October–November)
The year's biggest flights. Subterranean swarmers pour out of damp soil on the first warm day after a soaking rain.
- 2
Warm spring days (March–May)
A second, smaller subterranean window after spring rains. Flights often come in the morning.
- 3
Hot, still afternoons (August–October)
Drywood swarmers fly in the heat of the day. Smaller, quieter flights, often one house at a time.
- 4
The rest of the year
Colonies keep feeding year-round. Swarming is just the part you can see.
Which termite flies when
The two local species keep different calendars, because different triggers set them off. Western subterranean termites wait for the ground to soften. The first soaking fall rains, followed by a warm and calm day, bring the biggest flights of the year. A smaller window opens in spring after the winter storms. The colony lives in the soil, so whole neighborhoods often fly at once. For a week or two, wings show up on windowsills all over town.
Western drywood termites answer to heat instead. Their swarmers leave infested wood on hot, still afternoons in late summer and early fall. The flights are smaller and easier to miss. Often it’s one house at a time.
Before you act on either, rule out flying ants. They swarm after rain too, and people mix them up all the time. The check takes ten seconds. Termite swarmers have a thick, straight waist. Their four wings all match and run about twice the body length. Their antennae are straight, like a string of beads. Ants are pinched at the waist. Their front and back wings are different sizes. Their antennae have an elbow bend. Wings alone can settle it. Matching, oversized wings mean termites. Two wing sizes mean ants.
Which termite you saw matters as much as whether it was a termite at all. The species decides where treatment happens. If the swarmers are already gone, the drywood vs. subterranean guide can settle it from the evidence they left behind.
Swarmers indoors? Schedule the free inspection while the evidence is fresh.
If they’re swarming right now
Don’t spray. It feels useful, but it destroys the evidence. The swarmers will die on their own within a day. They’re weak fliers, and almost all of them fail. An inspector could have used them to name the species on sight. So collect a few in a zip-top bag instead, or take a sharp photo. Then note exactly where they came out. A stream from a baseboard gap, a window frame, or a garage wall points straight at the colony. Scattered wings can’t do that.
Then act while the evidence is fresh. Vacuum up the rest if you want. Just leave the spot where they emerged untouched, and book the free inspection. Swarm evidence plus an intact emergence point makes the diagnosis easy. The same house six months later, with the wings swept up, is much harder to read. And the colony is still eating the whole time.