Thermal equator

From Glossary of Meteorology

thermal equator

  1. Same as heat equator.

  2. (Rare.) The belt around the earth that is bounded by the mean annual isotherms of 27°C (80°F); also, the middle line of this belt.

  3. (Rare.) The belt of hottest temperatures around the earth as it annually migrates with the inclination of the sun.