Weather Blog

What is the Hottest Time of the Day?

I was asked this question by a viewer’s email today.  And I figured I could expand on the response here.

As the sun rises and climbs through the sky, the solar radiation gets more intense.  The sun is at its highest point in the sky at noon local time (1pm with Daylight Saving Time).   At that point, the sun’s rays will cause sunburn in the shortest amount of time.  But although the sun’s radiation is at its strongest then, that doesn’t mean that the temperature peaks at mid-day.

In fact, the temperature will continue to climb so long as the earth is receiving more incoming heat than the earth is radiating back to space.  The temperature will actually peak between 3 pm and 4:30 pm each afternoon, dependent to some extent on variable cloud cover and wind speed.  After that, as the sun gets lower in the sky, the temperature will begin to fall gradually back from its high, and the drop in temperature accelerates after sundown.

A very similar pattern occurs on a seasonal level.  The sun’s radiation is at its greatest for the entire year at the summer solstice, around June 20th.  But the earth continues to heat up after days on end of relentless summer sun.  And the temperature peaks not in late June, but in late July and early August.  This is sometimes referred to as the “Lag of the Seasons”.

Chief Meteorologist David Finfrock