Hurricanes Helene and Milton's floodwaters pose a silent danger: mosquito-borne diseases like malaria, dengue, Zika, and chikungunya. Climate change is extending the mosquito transmission season, increasing the risk of these diseases spreading in the U.S. Despite some vaccines, many countermeasures are lacking. The U.S. government could use advance market commitments to incentivize vaccine development, mitigating the spread of these pathogens.