(Newser) – The US will face a lot of hot air this week—and not all of it is coming from the Republican National Convention. Rather, a "heat dome" is about to settle over the country, bringing temperatures as high as 115 degrees in some areas, NBC News reports. According to the AP, the high-pressure system is forecasted to keep hot air trapped over the US, beginning Wednesday in the Midwest. From there it will spread toward both coasts, generating high temperatures and heavy humidity. The National Weather Service has already issued heat alerts for more than a dozen states. But, while 200 million people will face temperatures of at least 90 degrees, it could be worse. "We're not talking record-breaking heat by any stretch," one meteorologist tells the AP. "The only thing is it is the warmest it's been this summer, so in that respect people may not be prepared for it."