What’s the Best Kind of T-Shirt To Wear In A Heatwave?

Most of us just kind of know what we wear in the heat can affect how hot we feel.

Yet, it's not something I think most of us have thought about all that much. At least not beyond asking ourselves whether we should wear a dress shirt or a polo shirt. Shorts or Jeans. Slacks or a dress. Yet, the National Weather Service Office out of Kansas City did a little test during the heatwave we just experienced that shows exactly the best type of T-Shirt to wear when it's hot.

The NWS staff took three types of T-Shirts and placed them outside in the sun. The T-Shirts included a white cotton T-Shirt, a black cotton T-shirt, and a white polyester T-shirt. So which one do you think would be the coolest to wear?

I would have put my money on the white cotton T-shirt. I mean, it's pretty easy to know that even though you'll look the coolest in the black T-shirt, it's just going to soak up the sun. Plus, cotton is natural, so the white cotton T-Shirt is the one that'll be the coolest, right?

Wrong.

The white polyester T-shirt stayed the coolest. At 2:30 PM CDT, when the air temperature was 97, the black T-shirt was 24 degrees warmer than the air temperature. The white cotton T-shirt was 16 degrees warmer than the air temperature. While the white polyester T-shirt was only 11 degrees warmer than the air temperature.

The white polyester T-shirt also didn't heat up as quickly as the white cotton or the black cotton T-shirts. At 9:30 AM CDT, the first time the NWS measured the temperatures of the shirts, the white cotton, and white polyester T-Shirts were 88 degrees, while the black T-shirt was already five degrees warmer.

So does the NWS test hold up? First, I didn't bother to prove that a white or light-colored T-shirt is better than a black or dark colored T-shirt. I've proven that to myself just out walking around the Missouri State Fair, and I bet you have too. What I did want to look up is whether others thought polyester T-shirts were actually better.

It was hard to find proof because most of my search results were trying to sell me a T-shirt. Yet I did find a story from Outside Online that proved the NWS test. Outside Online says cotton shirts aren't bad, but that polyester is better:

Most polyester-based knits let moisture evaporate quickly, giving you lots of cooling when you’re active and keeping you dry once you’ve found a shady place to sit and rest.

This doesn't only prove the NWS test which was just proving how warm the T-shirt actually gets, but how it performs when the shirt is being worn. Interestingly enough, in a climate like Missouri, when it gets really hot and you're outside and active, there may not be a really good solution. "If you’re facing a climate that is both hot and humid, nothing is going to work that well. In that case, I’d suggest a synthetic shirt—at least you’ll stay a little bit drier than you would in cotton."

So there you have it, a polyester white T-shirt is best to wear when you're outside in the heat. Or perhaps, it's a better choice to just hang out in the air conditioning and binge-watch one of your favorite TV shows. Here's the results of the test performed by the National Weather Service in Kansas City posted on Facebook: