You've probably heard of the heat index, and you might be aware of the National Weather Service's HeatRisk tool, but do you know what a heat dome is? If not, it's the perfect time to learn -- nearly a third of the US is about to be exposed to temperatures above 100 degrees because of one.
The NWS has issued a bulletin warning that 100-degree temperatures will likely hit residents in the middle of the US today. The cause for that thermometer spike is a growing heat dome in the Mississippi Valley that should expand to the northeast by the end of the week, potentially affecting more than 100 million people, per Accuweather.
If "heat dome" is a new term for you, keep reading and I'll break down what it means and what causes it. For more help this summer, check out CNET's top 10 hacks for keeping your home cool in the summer or learn how to recognize the early signs of heatstroke.
What is a heat dome?
Think of a heat dome as similar to putting a lid on a pot or a frying pan while cooking something, Alex Lamers of the National Weather Service told NPR.
A heat dome is what happens when a high-pressure system lingers, causing hot air to become trapped under it, resulting in prolonged temperature spikes. Just like how putting a lid on a pot or pan traps the heat and cooks the food faster. Except in this case, the food is you and me.
This is made worse by the fact that high pressure systems are known to cause dry weather, which can also contribute to hotter temperatures.
According to the heat map provided on the National Integrated Heat Health Information System's official website, heat risks are elevated for most of the country between the Midwest and Lower Mississippi Valley regions and the East Coast, with eastern North Carolina, central Virginia, the Pittsburgh area, southeast Pennsylvania, southeast Maryland, most of New Jersey and almost all of Delaware being under extreme heat warnings.
In the hardest-hit areas, temperatures may go as high as 115 degrees, while others will hover between 95 and 100 degrees. All around, it's the kind of weather than can make the prospect of a power outage a life-or-death scenario.
How long do heat domes last?
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