BALTIMORE — It would be no surprise to say that sunny skies tend to warm us. There are, of course, exceptions, but we all feel the warmth in the sun. On the flip side, a cloudy day can end up cool. But have you ever wondered what clouds can mean at night? That's where radiational cooling comes in.
The short version is that clear skies and calm winds create colder temperatures. When we have clouds overhead at night, that can keep us warmer.
Let's start like this:
Energy from the sun travels 93.86 million miles to get to the surface of the earth. All that energy is absorbed and warms the surface first, then eventually the air above it. That is how we get into the low 70s on a nice spring day.
If those skies stay clear overnight that can cool us quickly.
All that heat that the earth absorbed is radiated back into the air at night. Warmer air always rises and if there are no clouds to "catch" that heat and send it back we cool a lot faster. Another factor for a cool night is calm winds. If there is a light breeze that can mix the air and keep the heat closer to the earth.
To sum it all up, clouds at night "trap" heat. Clear skies will cool us faster. And even a light wind can stop the heat from going straight up. These are just some general forecasting tools we use everyday!
