Mosquitoes are cold-blooded creatures, which means 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. Mosquitoes hibernate in the colder months, and when temperatures drop below 50 degrees Fahrenheit, they become more lethargic and eventually die. However, many mosquitoes have adapted to cold weather, and some species of mosquitoes have fully adapted to living in cooler climates. Mosquitoes that have winter-hardy eggs hibernate as embryos in eggs laid by the last generation of females in late summer. The eggs are usually submerged under ice and hatch in spring when water temperatures rise. Other kinds of mosquitoes overwinter as adult females that mate in the fall, enter hibernation in animal burrows, hollow logs, or basements, and pass the winter in a state of torpor. A hard or killing frost will kill virtually all exposed mosquitoes. A killing frost is defined as two consecutive hours at a temperature below 28 degrees Fahrenheit.