In the United States, mosquitoes are more of a seasonal nuisance than a widespread public health crisis, but some states offer far better breeding conditions than others. Here are the top 10 worst mosquito states in 2026, according to OutsideOnline.com. TEXASIn the Lone Star State, mosquitoes are just as much a part of summer as cowboy boots and barbecue. From the desert landscapes of Big Bend National Park to marshes and waterways across the state, mosquitoes are a familiar nuisance for hikers, campers and anglers alike. Home to 61 mosquito species, South Carolina's mosquito season typically runs from March through September.