Amphibians are cold-blooded. Cold-blooded animals, including amphibians, are also called "ectotherms." Their body temperatures are affected by outside sources, such as heat from the sun and local environmental conditions.
Because their internal temperatures are influenced by their surroundings, amphibians must engage in different behaviors depending on the ambient weather. When it's cold, they often expose themselves to the sun in order to warm up. In hot weather, they instead burrow into the ground during the daytime and emerge at night when it's colder. Other animals that are ectotherms include fish and reptiles. One of the advantages of being cold-blooded is that these creatures don't need to eat as much as their warm-blooded counterparts of a similar body size.