Yellow jacket season in the Bay Area follows a predictable cycle — and understanding it helps homeowners stay ahead of the problem before it becomes dangerous.
The Yellow Jacket Seasonal Cycle
Winter: Fertilized queen yellow jackets overwinter in protected spots — under bark, in debris, in attics, and in other sheltered locations. The colony is dormant.
Spring: Queens emerge and begin building new nests — typically just a few cells at first. This is the easiest time to address a problem because colonies are tiny and populations are low.
Summer: Colony populations grow rapidly as workers forage and expand the nest. Colonies that began in early spring can have hundreds of workers by midsummer.
Late Summer / Fall: Colonies reach peak size — sometimes thousands of workers. This is when aggression is highest, foraging is most intense (yellowjackets are attracted to food, protein, and sweet drinks at outdoor gatherings), and the risk of painful stings is greatest.
Where to Look for Early-Season Nests
In spring, watch for queen yellow jackets investigating:
- Gaps in siding or eaves
- Rodent burrow holes in the ground
- Spaces under decks and porches
- Compost and debris piles
A nest found and treated in spring can prevent a much larger problem in fall. ATCO provides yellow jacket assessment and removal throughout the Bay Area — contact us at the first sign of activity.