From now into September, their numbers will increase.
People run the highest risk of getting stung when they disturb the insects' nests.
Both bumblebees and yellowjackets will vigorously defend their nests. This can happen to gardeners while weeding a flower bed or digging in a vegetable patch. Bumblebees and yellowjackets nest in the soil. They often build in a hole, such as a hollowed-out spot in old railroad ties used for landscaping, or in gaps at the edge of retaining walls or driveways. There are far more yellowjackets in a colony, sometimes thousands in a single nest.