When Is Another Heat Dome Coming?

If you're a fan of extreme weather, you may have been frolicking in the sprinklers as temperatures skyrocketed in most of the United States this week. The rest of the miserable, sweaty masses, however, were all wondering the same thing: When is the next heat dome, so we can plan to flee the country in advance? Fortunately, there's good news on this (weather) front. The current spate of high temperatures has been winding down over the course of the week, and the National Weather Service is predicting rain and thunderstorms from the Mississippi valley to the mid-Atlantic states over the next few days. It looks like the current heat wave is over, and no weather services are anticipating another so-called heat dome anytime soon.

But that doesn't mean it can't happen again in the future, although there are several conditions that have to be met in order for it to be the case. First of all, it's important to understand how pressure affects weather. In a high pressure system, the air sinks; in a low pressure system, it rises. This week, the jet stream — a path of air flowing across the country — developed a ridge preventing cooler air from moving south and trapping a sinking high pressure system inside a "dome" of air. As you may recall from science class, compressed air heats up, causing the bubble of hot air over a large portion of the United States to get hotter. The result is a large, long-lasting heat wave across much of the country.

So the next heat dome won't happen until these conditions occur once again — hopefully not anytime soon, although meteorologist Mike Musher told Scientific American that high pressure systems aren't uncommon during the summer. "With the jet typically so far north and not much cold air to dig into the United States, it's natural for these large high pressure systems to develop," he said.

In the meantime, many meteorologists have taken issue with the term "heat dome," claiming that it's misleading. For one thing, the system isn't necessarily shaped like a dome; meteorologist Gary England told the New York Times that he usually refers to it as a "large zone of hot air." For another, "heat dome" isn't officially recognized in the National Weather Service glossary of terms. As The Daily Beast points out, many of the more catastrophic-sounding meteorological terms — "arctic death spirals," "thundersnow," and yes, "heat domes," — are used to provoke a sense of impending doom, even though they may be normal weather phenomena.

On the other hand, the heat wave across the United States was very real this week. Autumn can't come fast enough.