In San Diego, drywood termites swarm from late summer into fall, roughly September through November, on warm daytime hours, while western subterranean termites swarm in spring, typically February through May on warm afternoons after a soaking rain. Because San Diego’s coastal climate stays mild year-round, some swarm risk exists in almost every month, and seeing winged termites is the clearest sign of an active colony.
Termites are just one part of San Diego’s year-round pest cycle. For the full picture of which pests peak when, see our San Diego pest season calendar.
A swarm is a colony sending out its winged reproductives, called alates, to start new colonies nearby. If you see them inside your home or piling up on a windowsill, the colony is already established somewhere in or under the structure. The timing matters because it tells you which species you’re dealing with, and the two San Diego termites need completely different treatments.
The San Diego termite swarm calendar
Two species cause almost all termite damage in San Diego County, and they swarm at opposite ends of the year. UC’s Integrated Pest Management program confirms the broad windows: drywood termites swarm in summer and fall during daytime, and western subterranean termites swarm in spring or fall on clear days after a soaking rain. Here’s how that maps to the San Diego calendar.
| Season | Termite type | What you’ll see |
|---|---|---|
| Winter (Dec–Jan) | Low activity | Mild coastal days can still trigger small drywood flights |
| Spring (Feb–May) | Western subterranean | Dark swarmers on warm afternoons after rain, equal-length wings |
| Early summer (Jun–Aug) | Transition | Occasional drywood swarmers as heat builds, attracted to lights |
| Late summer to fall (Sep–Nov) | Western drywood | Peak drywood swarms on warm evenings and daytime, light-attracted |
The dates aren’t rigid. A warm spell can pull a swarm earlier, and a cool, dry stretch can delay one. What’s consistent is the pairing: spring swarms point to subterranean termites coming up from the soil, and fall swarms point to drywood termites already living inside your wood.
Western drywood termites (the coastal homeowner’s problem)
Drywood termites (Incisitermes minor) are the species most San Diego homeowners actually see. They live entirely inside the wood they eat, so they don’t need soil contact. Their swarmers emerge on warm days and evenings from late summer into fall, and they’re strongly drawn to lights, which is why you’ll find them at windows, porch fixtures, and screen doors. Older coastal homes with original Douglas fir framing in North Park, Coronado, La Jolla, and Mission Hills see the heaviest drywood pressure. For a deeper breakdown, see our guide on the signs of termites in San Diego homes.
Western subterranean termites (the spring-rain swarmers)
Subterranean termites (Reticulitermes hesperus) live in large underground colonies and travel up through mud tubes to reach wood. Their swarmers are dark and small, and they fly on warm afternoons in spring, usually within a day or two of a good rain. Homes with irrigation against the foundation in El Cajon, La Mesa, Escondido, and East County see the most subterranean activity. We cover the full split in our post on drywood vs. subterranean termites in San Diego.
What a termite swarm actually means
A swarm doesn’t mean the termites just arrived. It means a colony has matured enough to reproduce, which usually takes years. So if you see swarmers leaving your home, the infestation isn’t new, and the wood damage has been quietly progressing.
Most swarmers die quickly once they leave, and the discarded wings they leave behind on sills, counters, and floors are often the first thing a homeowner notices. A pile of identical clear wings near a window is a strong tell. If you’re finding them, the right move is a professional termite inspection to locate the colony before more wood is lost.
How to tell termite swarmers from flying ants
This is the single most common mix-up, and it’s easy to settle in a few seconds. Termite swarmers have straight, bead-like antennae, two pairs of equal-length wings, and a thick, straight body with no waist. Flying ants have bent (elbowed) antennae, front wings longer than the back pair, and a sharply pinched waist.
If the wings are all the same size and the body has no narrow middle, you’re looking at termites, not ants. We walk through it in detail with photos in flying ants vs. termite swarmers. Getting this right matters, because flying ants are a nuisance, but termite swarmers mean structural wood is at risk.
What to do if you see a swarm in San Diego
Don’t spray the swarmers and move on. Killing the visible winged termites does nothing to the colony producing them. Instead, capture a few in a bag or jar so the species can be confirmed, note where you saw them and the date, and avoid disturbing any mud tubes or pellet piles since those help an inspector locate the source.
Then schedule an inspection. The best time to book is just before your species’ swarm window, late spring or summer ahead of drywood season, and winter ahead of the spring subterranean flights, so problems get caught before they spread. An annual inspection is cheap insurance for older coastal homes and canyon-adjacent properties where humidity and aging wood-frame construction raise the risk.
If you’re buying or selling, a swarm finding will show up on the Wood Destroying Organism (WDO) report that almost every San Diego escrow requires. Understanding whether the activity is drywood or subterranean changes which termite treatment gets quoted, and what’s fair to negotiate. For budgeting, see our termite inspection cost guide for San Diego, and for keeping swarms from starting in the first place, our notes on termite prevention for San Diego homes.
Any pest control company you hire should be licensed by the California Structural Pest Control Board (SPCB), which you can verify at pestboard.ca.gov before work begins.
Frequently asked questions
When do termites swarm in San Diego?
Drywood termites swarm from late summer into fall, roughly September through November, on warm days and evenings. Western subterranean termites swarm in spring, typically February through May, on warm afternoons after rain. San Diego’s mild coastal climate means some swarm risk exists in nearly every month.
What months do drywood termites swarm in California?
Western drywood termites swarm during daytime in summer and fall, with San Diego activity peaking roughly September through November. They’re attracted to lights, so they often show up at windows and porch fixtures in the evening. A warm coastal stretch can occasionally trigger smaller flights earlier in summer.
Do subterranean termites swarm in spring?
Yes. Western subterranean termites swarm on warm afternoons in spring, generally February through May in San Diego, usually within a day or two of a soaking rain. They can also produce a smaller fall swarm. Their swarmers are dark, small, and have two pairs of equal-length wings.
Does a termite swarm mean I have an infestation?
Almost always, if the swarm came from inside or directly under your home. A colony only produces winged reproductives once it has matured over several years, so swarmers leaving your structure mean an established infestation, not a new one. Swarmers that simply fly in from outside and land are less alarming, but discarded wings indoors warrant an inspection.
What attracts termite swarmers?
Drywood swarmers are strongly drawn to lights, which is why they collect at windows, porch lamps, and screen doors after dusk. Subterranean swarmers are triggered by warmth and moisture, so they fly after spring rains when soil is damp. Both are looking for mates and a new place to start a colony, often the same wood they came from.
Should I worry about finding termite wings on my windowsill?
Yes, discarded wings are one of the clearest signs of an active termite colony. Swarmers shed their wings shortly after their flight, so a small pile of identical clear wings on a sill, counter, or floor usually means a colony is nearby. Save a few wings or swarmers and schedule an inspection to confirm the species.
If you’ve spotted swarmers, discarded wings, or mud tubes anywhere on your property, don’t wait for the damage to spread. Call us at (858) 925-5546 for a free termite inspection in San Diego County, and we’ll identify the species, locate the colony, and document everything clearly for homeowners and real estate transactions. You can also start with our San Diego pest control service area.