September in the Valley

The San Fernando Valley pest calendar

Sam Karbelnig has treated Valley homes since 2005. This is when each pest actually shows up here, month by month, and what to do before it does.

Last updated September 18, 2026Reviewed by Sam Karbelnig, owner

Month by month

Quiet Busy PeakTap a month
September
This monthGet a quote for wasps
Peaking

Wasps, Ants, Spiders

Rising or notable

Rats and mice, Termites

Yellow jackets are at their most aggressive as colonies reach full size and food gets scarce before fall, so late summer stings spike hard in September. Ants and spiders stay elevated in the lingering heat. Rodent activity starts climbing again as nights begin to cool, and drywood termites swarm as summer turns toward fall.

What to do in September

Keep food and trash covered outdoors, give any ground nests a wide berth, and watch for termite swarmers or pellet piles around wood trim.

Every pest, every month

Sort by
Pest activity by month in the San Fernando and Conejo Valleys, from Facility Pest Control service records, 2005 to 2026. Red is peak, amber is rising, pale is low, white is none.
PestJanFebMarAprMayJunJulAugSepOctNovDec
Ants
Bed bugs
Bees
Cockroaches
Crickets
Earwigs
Fleas and ticks
Gophers
Mosquitoes
Rats and mice
Scorpions
Snakes
Spiders
Termites
Wasps and yellow jackets
Season by season

What to do, season by season

Winter
December to February

Rodent proofing while attics are quiet, gopher treatment in the wet soil, and the first bee swarms in late January. The best three months to book exclusion work.

Rodent control
Spring
March to May

Bees and wasps build, gophers are at their busiest, ants arrive after rain and termites swarm. Most Valley homes start the exterior barrier in March or April.

Get a quote for spring service
Summer
June to August

The general pest peak. Mosquitoes, ants indoors for water, cockroaches, yellow jackets turning aggressive, and scorpions on hillside lots in August.

Mosquito stations
Fall
September to November

Yellow jackets at their worst, spiders on the eaves, drywood termite swarms, and rat season beginning. Seal the roofline in September and October stays quiet.

Rat season prep
Share it

Embed or share this calendar

Local news sites, HOAs and neighborhood groups can embed the month by month band on their own pages. It updates when Sam updates it.

<iframe src="https://facilitypestcontrol.com/seasonal-pest-calendar/embed/" width="100%" height="260" title="San Fernando Valley pest calendar by Facility Pest Control"></iframe>
When is rat season in Los Angeles?

In the Valley, October through February. Roof rats move indoors on the first cool nights in September and stay until the attics warm up in March. The busiest rodent months at Facility Pest Control are October and November, every year since 2005.

When do bees swarm in the Valley?

Swarm season starts in the last week of January and runs through May, peaking in March and April. A swarm on a fence or in a water meter box in February is normal. Wasps and yellow jackets are a different story, they build through spring and turn aggressive in July, August and September.

When should I start mosquito treatment?

May. Mosquitoes show up in April, peak June through August, and hang on through September. In2Care stations installed in May cover the whole season and do not harm bees.

Ready when you are.

Call, text, or send a quote request and Katie or Sam calls you back during office hours. No visit fee, no contract.

CallTextGet a free quote