The hottest part of the day during the summer is between 4 p.m. and 6 p.m. The earth starts to radiate heat back into space.
SACRAMENTO - There's a misconception that the warmest time of the day is noon. It may feel hotter at the noon hour because we are getting the most energy from the sun at that time.
However, Earth is storing incoming energy or heat throughout the day. The longer the sun is out, the warmer the air becomes. Temperatures will continue to climb as long as Earth is receiving more incoming heat than it is radiating back into space. The re-radiation happens later in the day, making the hottest part of the day between 4 p.m. and 6 p.m. during the summer.
Temperatures will warm very quickly during the morning hours because of the mixing of two air masses. Overnight, cooler air sinks to the valley from the mountains. As the sun rises, the solar radiation heats the ground. The difference in temperature between the two air masses creates turbulence which results in the quick warm-up. For example, the temperature at Sacramento Executive Airport was 65 degrees at 7 a.m. The temperature jumped 20 degrees three hours later.