Characteristics of the Underground Atmosphere

Many of the familiar roadside signs advertising caves open to the public carry the phrase, “Come underground and cool off”. This is reasonable advice, for during the heat of summer the temperature of these caves is indeed pleasantly cool. If the principal tourist season were in the winter instead of the summer, however, the signs would probably read, “Come underground and warm up”, for in winter these same caves are far warmer than the surface. Cave temperatures are nearly constant throughout the year.