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thermal equator[′thər·məl i′kwād·ər]
(also heat equator), the parallel of latitude having the highest mean air temperature at the earth’s surface over a period of many years. In January the thermal equator coincides with the geographic equator; the mean air temperature here for January is approximately 26°C. In July the thermal equator shifts to 20°–25° N lat., where the mean air temperature is approximately 28°C. The mean annual position of the thermal equator is near 10° N lat. The thermal equator shifts northward from the geographic equator because the tropical regions of the northern hemisphere have a larger land area than those of the southern hemisphere and land is more strongly heated than ocean water.