Termite Swarming Season in Southern California: When to Expect It
Termite Swarming Season in Southern California: When to Expect It
Termites don't follow one swarming season in Southern California, because the timing depends on which species you're dealing with. Subterranean termites swarm during the rainy months of fall through spring, drywood termites swarm in late summer into fall, and Formosan termites swarm on warm, humid nights in late spring through summer. If you've spotted winged insects near your windows or lights, the time of year you saw them is actually one of the best clues to which species is involved, and how urgently you need an inspection.
If you're seeing signs beyond just a swarm, like mud tubes, hollow-sounding wood, or discarded wings inside the house, this guide to termite signs breaks down which symptoms point to which species in more detail.
Subterranean Termite Swarms: Fall Through Spring
Western subterranean termites, the most common termite species across Southern California, typically swarm during the day in the local rainy season, from fall through early spring. Swarms tend to cluster around warm days that follow rainfall, so activity can spike unpredictably during a wet winter and stay quiet during a dry one.
What to look for:
- Swarms happening during daylight hours, often mid-morning
- Discarded, uniform-length wings collecting near windows, doors, or foundations after a swarm
- Mud tubes, thin tunnels made of soil and saliva, running up foundations or exterior walls near where swarmers were seen
Drywood Termite Swarms: Late Summer Into Fall
Western drywood termites swarm during daylight hours, typically from late summer into fall, often on warm, dry afternoons. Unlike subterranean termites, drywood termites don't need soil contact and live entirely inside wood, so their swarms are more directly tied to warm, dry conditions than to rainfall.
What to look for:
- Swarms during warm afternoons rather than after rain
- Small, pellet-like droppings (frass) that look similar to coffee grounds or sawdust, a telltale sign specific to drywood termites
- Swarmer activity near attics, eaves, or exposed wood trim, since drywood colonies often start in these areas
Formosan Termite Swarms: Late Spring Through Summer
Formosan termites swarm at dusk or after dark, typically from late spring through summer, on warm and humid evenings. Formosan termites were once considered rare in Southern California, but UC Riverside entomologists have confirmed colonies in Los Angeles County itself, including in Highland Park, Hollywood Hills, and La Verne, in addition to earlier detections in San Diego County. Their colonies can grow far larger than native subterranean colonies, and a mature colony can consume significantly more wood per month.
What to look for:
- Swarms at night, often around outdoor lighting
- A lighter-colored body compared to native subterranean termite swarmers
- Rapid or unusually extensive wood damage, since Formosan colonies feed at a faster rate than other local species
Why Termite Swarms Happen at Different Times of Year
Swarming is how a mature termite colony reproduces. When conditions are right, usually a warm day following rain or humidity, winged reproductive termites (called alates) leave the colony in large numbers to start new colonies elsewhere. Each species has evolved to swarm under different weather triggers, which is why the timing varies so much by species rather than following a single "termite season."
Seeing a swarm doesn't mean you have a new problem. It usually means an established colony has been present for a while already, since colonies typically need to mature for a few years before they're capable of swarming.
Termite Swarm Season at a Glance
| Species | Typical Swarm Timing | Time of Day | Trigger |
|---|---|---|---|
| Western Subterranean | Fall through early spring | Daytime | Warm day after rain |
| Western Drywood | Late summer into fall | Daytime | Warm, dry afternoons |
| Formosan | Late spring through summer | Dusk/night | Warm, humid evenings |
Because swarm timing depends on weather rather than a fixed calendar, activity can start earlier, run later, or overlap between species in any given year.
What to Do If You See a Termite Swarm
- 1 Don't clean up all the evidence. A few discarded wings or a sample of the insects themselves can help a technician confirm the species during an inspection.
- 2 Note the time of day and conditions. Whether the swarm happened during the day or at night, and whether it followed rain or a warm stretch, helps narrow down which species is involved before an inspection even begins.
- 3 Schedule an inspection rather than waiting. Since swarming indicates a colony has likely been established for some time, the sooner an inspection happens, the sooner you'll know the extent of any damage and the right treatment path.
Frequently Asked Questions
It depends on the species. Subterranean termites swarm from fall through early spring after warm rain, drywood termites swarm from late summer into fall on warm afternoons, and Formosan termites swarm from late spring through summer on warm, humid nights.
Yes, in almost all cases. Swarmers only emerge from colonies mature enough to reproduce, which typically means the colony has already been established on or near the property for some time.
The time of day and season are strong clues: daytime swarms after rain point to subterranean termites, daytime swarms in late summer or fall point to drywood termites, and nighttime swarms in warm weather point to Formosan termites. For a closer look at the specific signs each species leaves behind, see 9 Signs of Termites in Your Home (and How to Tell Which Type You Have). A professional inspection can confirm the species and the extent of any colony activity.
Both. Swarmers often emerge outdoors first, but if a colony is established inside a wall void or attic, swarmers can emerge directly inside the home, frequently near windows, light fixtures, or vents where light is visible from inside the colony.
Most swarms are brief, often lasting only 30 minutes to a couple of hours, since swarmers only survive a short time after leaving the colony before shedding their wings, pairing off, and either starting a new colony or dying. A property can still experience multiple separate swarm events across a season.
Termite swarmers have straight antennae, a thick waist, and two pairs of wings that are equal in length, while flying ants have bent antennae, a pinched waist, and uneven wing lengths. Since both can appear seasonally and look similar at a glance, comparing these features closely (or having a technician confirm) is the most reliable way to rule out flying ants before assuming termite activity.