Cody Flom, 12, suffered a fatal heat stroke while hiking Friday at the Sonoran Mountain Preserve in Arizona, where temperatures soared to a sweltering 111 degrees, a Phoenix Fire Dept. spokesperson said.
Heat indexes well over 100 degrees are expected across dozens of states in the nation's central and eastern portions, the National Weather Service forecasts. A heat index, or the "feels like" temperature, combines the effects of temperature and humidity on the human body.
Temperatures also could reach the century mark Monday afternoon in New York and Washington, and it's going to be hot in Philadelphia this week for the Democratic National Convention. The mercury will hit the middle to upper 90s through the middle of the week but high humidity will make it feel like it's in the triple digits.
Heat dome to blame
The "heat dome," a high pressure system that causes hot air to stay trapped in the atmosphere, has nearly 54 million people under excessive heat warnings across 12 states, CNN meteorologist Sean Morris said.
The sweltering Midwest weather claimed the lives of a handful of people in the Detroit area over the course of three days, Roseville Police Chief James Berlin told CNN.
Five elderly residents who had underlying health issues died as a result of the sky-rocketing temperatures, Berlin said. Residents were encouraged to stay hydrated and find an air-conditioned place to avoid heat exhaustion or heat stroke.
Detroit police and firefighters are doing their part to help residents beat the summer heat. They're offering rides to cooling centers set up at the city's recreation center and public library and distributing water to residents.
Heat is one of the country's leading weather-related killers, and each year dozens of Americans die from overexposure
to high temperatures, according to The National Weather Service.
Hot, dry and breezy conditions across the West Coast have also hampered efforts to contain the rapidly expanding Sand Fire
. The fast-growing wildfire, which was only 10% contained Sunday, has consumed more than 33,000 acres.
Warmest half-year on record
Scientists note the record temperatures across the country could be part of a long-term global warming phenomenon. Last week NASA announced that every month in 2016 has been the hottest ever recorded
Global temperatures were on average 1.3 degrees Celsius (2.4 degrees Fahrenheit) higher than average between January and June this year when compared to the late 19th century, NOAA said.