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Why did it get colder after sunrise today?

Why did it get colder after sunrise today?
Photos: Frost in Southwest Florida
Posted at 4:25 PM, Feb 04, 2021
and last updated 2021-02-04 16:30:18-05

Southwest Florida woke up to some frigid temperatures this morning. Most people would probably think temperatures would gradually increase as the sun comes up, right? But it doesn't always happen that way.

For example, the temperature in Punta Gorda consistently stayed at 37° for several hours overnight, but it dropped to 36° just as the sun started to rise. Temperatures didn't increase until almost an hour after the sun had already been up.

This is called radiational cooling. Once the sun sets, the ground and air at the surface release all the energy it's collected from the sun throughout the day. Usually, clouds act as a blanket to help keep some of the warm air closer to the surface. Yet, we've had clear skies and plenty of dry air in the upper atmosphere over the past several days. This helped our temperatures dip even more this morning.

As the sun rises over the horizon, it starts to warm the surface a little more. However, the sun is still pretty low to the horizon, so the radiation is still weak. This sometimes allows temperatures to dip even after the sun comes up. Once the sun starts to really heat the cooler air at the surface, the warmer air will rise and the mixing process starts all over again.