What mechanism explains why the hottest day in the Northern Hemisphere usually occurs several weeks after the summer solstice?

Answer

Thermal inertia

The discrepancy between the longest day and the hottest day is attributed to thermal inertia, as oceans and landmasses take time to absorb and reradiate the massive amounts of solar energy collected.

What mechanism explains why the hottest day in the Northern Hemisphere usually occurs several weeks after the summer solstice?
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