Why Eastern Half Of The US Feels Like An Oven This June: The “Heat Dome” Explained

Tens of millions of people in the US are still up to their necks in an intensifying heatwave. This week, a “heat dome” parked over central and eastern regions is driving possible triple-digit temperatures and oppressive humidity, set to turn half of the country into a sweltering, sauna-like oven.

The Midwest and eastern US are set to bear the brunt, with “extreme risk” temperatures forecasted across several states on Tuesday, June 24, and Wednesday, June 25, according to the National Weather Service. 

This includes many of the highly populated cities – including Washington, D.C., Baltimore, Philadelphia, and New York – where dangerous heat levels are expected to intensify. Further west, urban areas in the Midwest and Upper Appalachian regions — including Cleveland, Columbus, Pittsburgh, Cincinnati, and Indianapolis — are also set to face intense heat, with temperatures soaring well above seasonal norms.

Temperatures are forecasted to start subsiding towards the latter half of the week, but will remain high. Further south, temperatures are not expected to be quite as hot, although uncomfortable conditions may persist beyond midweek, intensified by stifling humidity. 

Temperatures nearing or surpassing 37.7°C (100°F) are expected to be seen over three dozen states on Tuesday, and threaten to topple decades-old records, according to AccuWeather. 

More than 53 million people in the US have been under heat alerts since the weekend, but that figure is set to rise as the week rolls on. AccuWeather estimates that up to 170 million Americans are likely to experience incredibly hot temperatures in the last week of June. 

Don’t expect the sunset to bring much cooling relief, either. Nighttime temperatures may stay above 26.7°C (80°F), especially in some urban areas.

What is a heat dome?

The mid-summer temperatures will be given an extra boost from a weather phenomenon known as a heat dome, similar to the one that caused the freakishly hot heatwave of June 2021. This involves a high-pressure system that stays parked in one location for a prolonged amount of time, ensnaring very warm air and stopping any cool marine air from entering, like a bubbling saucepan with a lid on. The high pressure also pushes warm air down towards the ground and heats it further by compressing it.

That’s why it can feel like being in an oven: the landscape is effectively sealed inside a bubble of heat, with nowhere for the warmth to escape.

Climate change is likely to be another factor making this weather even more intense. Science has shown that heatwaves like this are becoming hotter, longer, larger, and more frequent as a result of human-driven global warming.

For more information on how to stay happy and healthy through heatwaves, check out the resources at https://www.ready.gov/heat. Stay hydrated out there.