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The Coldest Time of the Day

When the sun first rises in the morning it doesn't get warmer right away, but actually feels colder. Learn more on this Moment of Science.

Sunrise at the beach

Photo: shoebappa (flickr)

Right when the sun rises, its first rays are weak, making it feel colder until the rays become stronger as the day goes on

It seems natural to assume that as the sun rises in the morning, the temperature begins increasing.

However, when the sun first rises it doesn’t get warmer right away, but actually feels colder.

In fact, barring any storm fronts, the coldest time of day is sometime just after dawn.

The sun is kind of like a microwave, and the ground is kind of like a frozen TV dinner. The earth absorbs some heat from the atmosphere during the night. Sort of like putting your dinner out to thaw, but during the day, the sun acts like a microwave and quickly heats up the ground. Once the sun sets, the ground cools off by radiating heat out to the atmosphere and some escapes into space. Just as when the microwave stops, your dinner starts to cool down.

At dawn, the first rays of sunshine are weak. It takes time for the incoming radiation from the sun to counteract the rate that the ground is losing heat. Contrary to what you might think, that means the temperatures are coldest after dawn. It doesn’t get warmer until the sun is stronger and the ground starts to absorb heat again.

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