The San Gabriel Valley Pest Calendar: What Shows Up, and When
Twelve years of route days teach you the valley's rhythm. Here's what to watch for, season by season — and when to call before it peaks.
San Gabriel Valley pest pressure follows a predictable yearly rhythm: termite swarms in spring (typically March through May, after warm rains), ant surges plus wasps, mosquitoes and ticks through summer, crickets and rodents pushing indoors in fall, and rats, mice and roaches nesting through winter. The smart move is acting before each peak — the fall seal-up is the single highest-value pest visit of the year.
Pest pressure in the San Gabriel Valley follows a predictable yearly rhythm. Knowing what's coming lets you get ahead of it instead of reacting — here's the year, season by season. The most dramatic entry on the calendar: the first fall storm, when flooded Argentine ant nests move indoors overnight.
MONTH-BY-MONTH
| Month | Most active in the SGV | The smart move |
|---|---|---|
| January | Rodents nesting indoors; pillbugs & millipedes after rain | Seal entry points; fix leaks |
| February | Rodents; subterranean swarms possible after rains | Check foundations for mud tubes |
| March | Ants waking; ticks in green brush; swarms after warm rains | Walk the perimeter; watch for wings |
| April | Mosquitoes begin; ants build; wasps start nests | Dump standing water; knock down starter nests |
| May | Ant surges; spiders; fleas ramping up | Perimeter treatment; pet flea preventives |
| June | Ants peak with heat; wasps; mosquitoes | Keep sweets sealed; check patio eaves |
| July | Ants; wasps building to peak; mosquitoes | Weekly water-dump walk; mind the trash lids |
| August | Drywood swarmers begin; wasps peak; crickets start | Watch sills for wing piles; garage door gap |
| September | Drywood swarms; crickets; rodents begin pushing in | Inspect eaves; start the fall seal-up |
| October | Rodents push indoors; ticks resume; crickets | Finish exclusion before the rains |
| November | Rodents peak indoors; ticks in damp brush | Listen for attic noise at dusk |
| December | Rodents; moisture pests in damp rooms | Fix leaks; store boxes off the floor |
Spring (March–May): swarm season
Warm afternoons after rain send out termite swarmers — piles of identical wings on sills are the giveaway (here's how to read the signs). Argentine ants wake up hungry and head indoors, and spider egg sacs start hatching around the eaves.
Summer (June–August): the ant surge
Heat drives ant colonies indoors chasing water, spiders work the porch lights, and dry brush sends ticks hunting for hosts. This is peak season for maintenance plans — and the time most kitchen ant trails appear.
Fall (September–November): the great indoors
Cooling nights drive crickets into garages and rodents into attics and walls (often roof rats from fruit trees). The fall seal-up — sealing the gaps before animals move in — is the single highest-value pest visit of the year, especially for foothill-edge homes.
Winter (December–February): nesting season
Rats and mice settle into warm attics, and roaches hug warm plumbing. The quiet months are also the smart time to book termite work — and to think about what next spring's swarm season will bring (see the cost guide on why a plan beats one-offs).
Quick Answers
Quick Answers.
When do termites swarm in Southern California?
Mostly spring — warm, calm afternoons after rain, typically March through May — though drywood termites can also swarm in late summer and fall in the San Gabriel Valley.
What time of year are ants worst?
Summer. Heat pushes Argentine ant colonies indoors chasing water, which is why June through September brings the classic kitchen ant trails across the SGV.
When should I worry about rodents?
Fall and winter. As nights cool, rats and mice move into attics and walls, so a fall seal-up — sealing entry points before they get in — is the most valuable preventive visit of the year.
Is winter a good time for pest control?
Yes — it's an ideal, often-overlooked time to book termite work and get ahead of spring swarm season, since activity is quieter and scheduling is easier.
About the Author
Joshua is the owner and licensed operator of ExterMetro Termite and Pest Control in Arcadia, CA. He holds California SPCB Company Registration #8828 (Branch 2 & 3), is a licensed WDO inspector, and has worked San Gabriel Valley homes and businesses for over twelve years — hands-on in the field on every kind of job the valley throws at him.
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