This June was the hottest one on record, with temperatures more than 2 degrees above the 20th-century average for the month, according to the National Oceanic and Atmospheric Administration. NOAA's records stretch as far back as 1880.
The average temperature in Maryland last month was 75.2 degrees, 4.7 degrees warmer than normal. Virginia suffered through an average temperature of 76.1 degrees, 5.1 degrees higher than usual. And Arkansas averaged 81.7 degrees for the month, 5 degrees warmer than the 20th-century average.
The sizzling statistics have translated into a number of fatalities across the country, with many states and cities that register record-breaking temperatures leading the pack.
Maryland reported its 17th heat-related death Monday when a 20-year-old man went into cardiac arrest while cycling. Across the border in Virginia, the heat has contributed to nine deaths, and Washington, D.C., has reported one heat-related death.
Elsewhere, New York City has blamed three deaths on the heat; Philadelphia, 14; and Little Rock, Ark., four.
Some experts expect the death tolls to rise as the summer heat rolls on and medical examiner offices investigate more cases.
Despite some contention over what constitutes a heat-related death, many across the country find the growing numbers alarming.
"We're seeing increased numbers of heat-related illnesses earlier in the summer than expected," said Dr. David Markenson, chairman of the American Red Cross Advisory Council on First Aid and Safety.
"We haven't hit normal peak season but already [the numbers] are higher than past years," he said, adding that he believes the U.S. death toll from heat could pass 1,000 by year's end.
Despite the June 2010 record, however, 2006 was the hottest year to date, according to the National Oceanic and Atmospheric Administration.
That year, states across the country reported some of their hottest summers and summer months on the books: In Illinois and New York, for, instance, it was more than 3 degrees hotter than usual. California was 2.8 degrees hotter than average, with June alone a striking 4.3 degrees higher.
The United States also saw 253 heat-related deaths, the highest number reported for a single year so far this century, with the same states reporting some of the highest body counts: 65 in California, 42 in New York and 42 in Illinois, a sign that the devastating heat wave and resulting deaths spanned the country that year.
But high temperatures haven't always produced corresponding death tolls.
Indeed, the most heat-related fatalities for a single year occurred in 1995 with 1,021 deaths, including about 700 Chicagoans in a public health nightmare that shocked America.
The mean temperature for the summer of '95, however, was 72.7 degrees, making it the sixth coolest summer in the past 20 years.
Markenson warned that focusing on temperature statistics can be misleading.
"Temperature by itself is not necessarily the only factor," he said, pointing instead to heat index. "The combination of temperature, wind, and humidity determine how your body reacts to heat."