Adults have smooth, moist skin that is brown or reddish-brown in color with black flecks on their backs, sides and legs. They may also have a dark colored mask. Adults have red underlegs, hence their name. Females, growing to four inches in length, are almost twice the size of males.
Adult red-legged frogs like cool damp coniferous or deciduous forests and forested wetlands. During the non-breeding season, adult frogs spend most of their time on land in woodlands along streams, in moist sedge or brush, along shaded pond edges or under logs and other forest debris. Damp weather permits them to venture away from their primary water source into areas that would normally be too dry. They are inactive if temperatures are too cold or weather is too hot and dry. Coastal populations may remain active throughout the year.