Mosquitoes are cold-blooded creatures, meaning they cannot regulate their internal temperature, and their temperature is essentially the same as their surroundings. Mosquitoes function best at 80 degrees Fahrenheit, become lethargic at 60 degrees Fahrenheit, and cannot function below 50 degrees Fahrenheit. When temperatures drop below 50 degrees Fahrenheit, it causes some mosquitoes to become inactive and eventually die. However, many species of mosquitoes have adapted to cold weather and can hibernate or migrate to warmer areas. According to WebMD, the temperature at which mosquitoes can no longer function is around 50 degrees Fahrenheit. Mosquito eggs can survive in 50-degree weather or even much lower, and they are perfectly capable of waiting for the right conditions to hatch. Therefore, while cold weather can kill some mosquitoes, it may not be enough to eliminate the entire population.