Does a cold winter suppress wasp numbers?
Probably not. Overwintering queens are fully adapted to the local climate so even an unusually cold winter probably does not significantly increase their mortality. Plus, even if queen mortality is higher the surviving queens likely have more success, and bigger nests (same reason cited above). The factor that does suppress yellowjacket numbers in late summer is spring weather. Cold, wet springs tend to interfere with nest initiation while warm, dry weather tends to help it along. These effects can be very localized, however.
