What seasonal pests should I worry about after winter ends?

As winter loosens its grip, homeowners tend to notice two very different populations becoming active at once, and it's easy to read both as new problems when neither one is. The first is the overwintering insect group — Asian lady beetles, cluster flies, stink bugs, boxelder bugs — that entered the house last fall specifically to wait out the cold. The second is rodent activity around the foundation and yard that was there all winter but becomes easier to spot as snow melts and animals move around more in warmer weather. Both are the tail end of a story that started months earlier, not a fresh invasion arriving with spring.

The same warming and lengthening daylight that triggered fall entry behavior works in reverse come spring. Colorado State University Extension describes cluster flies moving "outdoors in early spring" once the warming trend holds, and the same general pattern applies to the other overwintering insects in this hub — they come out of diapause, become noticeably more active, and head toward windows and light sources trying to get back outside. This is a good-news phase in most respects: these insects aren't reproducing indoors and aren't causing damage, and the population you're seeing head for the windows is naturally thinning out on its own as it successfully exits.

Rodents are a different story, because — as covered in depth elsewhere in this hub — they don't hibernate and their indoor breeding doesn't pause for winter the way outdoor breeding does. What changes in spring is visibility: snow melts, animals range farther as temperatures rise, and any population that quietly grew indoors or near the foundation over winter becomes easier to spot through fresh droppings, gnaw marks or activity outdoors. That's exactly why early spring is worth treating as an inspection window rather than a relief — it's the best time to assess what actually happened over winter and address it before the next fall's entry push begins the cycle again.