What Causes a Heatwave?

The Farmers’ Almanac is calling for steamy, stormy, and sultry weather for many regions of the U.S. and Canada this summer. Depending on how you feel about heat, that may or may not be welcome news.

But what causes a heatwave, anyway? Why can we have a wet, chilly summer one year and a sizzler the next? Or even between one week and the next?

What Causes A Heatwave?

According to NOAA, a heatwave is defined as a period of unusually hot weather that typically lasts two or more days. To be considered a heatwave, the temperatures have to be outside the historical averages for a given area.

A heatwave occurs when a system of high atmospheric pressure moves into an area and lasts two or more days. In such a high-pressure system, air from upper levels of our atmosphere is pulled toward the ground, where it becomes compressed and increases in temperature.

This high concentration of pressure makes it difficult for other weather systems to move into the area, which is why a heatwave can last for several days or weeks. The longer the system stays in an area, the hotter the area becomes. The high-pressure inhibits winds, making them faint-to-nonexistent. Because the high-pressure system also prevents clouds from entering the region, sunlight can become punishing, heating up the system even more. The combination of all of these factors come together to create the exceptionally hot temperatures we call a heatwave.

How Heatwaves Can Be Deadly

While the phrase “dangerous weather” may conjure up images of blizzards, hurricanes, or tornadoes, it’s important to remember that heatwaves can be deadly. During a heatwave, you can protect yourself by staying out of the sun during the hottest parts of the day, avoiding strenuous activities, and keeping yourself hydrated with plenty of fresh water.

And when humidity and dew points are high along with the temperatures, things can get very uncomfortable!

Jaime McLeod

Jaime McLeod is a longtime journalist who has written for a wide variety of newspapers, magazines, and websites, including MTV.com. She enjoys the outdoors, growing and eating organic food, and is interested in all aspects of natural wellness.

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