From Coat To T-Shirt In The Same Day

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Fall is, undoubtedly, one of the hardest seasons to dress for.

In the morning, you’re shivering and breaking out the winter coats, and by the afternoon, you’re carrying around your coat and wishing you'd worn shorts.

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T​his weekend is a prime example: Temperatures on Sunday are going to rise over 20 degrees from morning to afternoon for many people in the eastern U.S.

But why does the temperature change so much over the course of a single day?

The main driver of this annoying trend is that the air is colder and, therefore, drier.

Warm air can hold much more moisture than cold air, which is what causes muggy misery during the summer for many regions.

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When things start to cool as we move further into fall, the air can hold less moisture and becomes drier.

Moist air absorbs and holds heat better than dry air, so when the atmospheric moisture content goes down, the atmosphere has a harder time holding onto the heat it collects during the day.

Dry air also means no clouds, and clouds act as insulators for the earth’s surface. During the day, clouds block solar radiation and keep high temperatures lower.

Just like the sun, Earth emits radiation in the form of heat, and on cloudy nights, that long-wave radiation gets trapped beneath the clouds, keeping the overnight lows higher.

Taking clouds out of the temperature equation removes a barrier to daytime heating and overnight cooling, so temperatures are able to fluctuate much more intensely than when clouds are present.

Hence, this weekend's mornings will feel wickedly wintry, but the afternoons will be perfect for a festive fall outing.

Sara Tonks is a content meteorologist with weather.com and has a bachelors and a masters degree from Georgia Tech in Earth and Atmospheric Sciences along with a masters degree from Unity Environmental University in Marine Science.