What Is A Heatwave?

One person’s insufferable heat can be another person’s typical afternoon, depending on where you live. Due to how people become acclimated to different climates, heatwaves do not have strict temperature values.

The most general definition of a heatwave is a period of unusually hot weather that lasts for at least two or three days. This goes off of how warm a location is compared to the long-term average temperature. So while temperatures may only need to reach 90 to 95 degrees to be considered part of a heatwave in the northern U.S., higher values closer to 100 to 105 degrees are needed to qualify for a heatwave in much of the southern states. Even hotter temperatures are required in the Desert Southwest.

Heatwaves form when a ridge of high pressure becomes established over a region. The warm, sinking air aloft allows surface temperatures to build underneath it. These can be fairly common over the southwestern and south-central U.S. during the summer months, sending high temperatures well into the 90s and 100s.

These ridges of high pressure can be long-standing features over a large part of the country, which can cause heatwaves to last several days to weeks at a time.

Humidity also plays a role in classifying a heatwave. When coupled with moist air, temperatures over 80 degrees can feel even hotter, known to many as the Heat Index. Depending on how humid it is, the increased moisture can make it feel several degrees hotter than the actual temperature.

Whether your threshold for a heatwave is 90 degrees or 110 degrees, be sure to make sure you have plenty of fluid and ways to cool off during a heatwave, and be aware of the symptoms of heat exhaustion and heat stroke.
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Story Image: A picture of a thermometer. (Pixabay via Gerd Altmann)