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.
Record-Breaking Temperatures May Boost Heat-Wave Death Toll
"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."
When it is hotter, more humid, and less windy, we are more likely to experience dehydration, loss of electrolytes, and even heat stroke, he said.
In addition, it is important to look at where temperatures occur, he added. How hot it is compared to how hot it usually is, which varies by region, may cause more fatalities as people are not aware of the heat's deadly power or what to do in response.
Tips to Beat the Heat Wave
Dr. Corey Slovis, chairman of the Department of Emergency Medicine at Vanderbilt University Medical Center in Nashville, Tenn., included two more elements: time and nighttime.
"Multiple days in a row, plus high humidity, plus nights when temperatures don't cool down," he said, "that's when we're most likely to see high numbers of heat illnesses and deaths."
Record-breaking or not, prolonged high temperatures and increased humidity are always a serious threat, especially for the elderly, infants, the mentally ill and people with chronic diseases.
More importantly, the public should consider the heat index, Markenson of the American Red Cross Advisory Council said, and pay greater attention to heat advisories.
Unfortunately, many people tend to ignore or disregard such warnings, and a few suffer the fatal consequences of doing so.
About half of adults 65 and older do nothing to change their behavior or reduce the risk of heat-related death during a heat advisory, according to a 2007 report in the International Journal of Biometeorology.
At the same time, those who are younger often believe they are not at as great a risk because of their age.
But between 1999 and 2003, almost 3,500 people died in heat-related deaths in the United States alone. The Washington Post reported Tuesday that, "high temperatures claim more lives in the United States than tornadoes, hurricanes, floods and lightning combined -- about 700 a year."
And as the U.S. population continues to age, the number of people who are vulnerable will continue to expand, making education and stronger resources all the more important.
Still, some are hopeful that America has seen the dawn of a new day in terms of awareness.
"I'm always worried about continued heat," Vanderbilt's Slovis said, "but I'm optimistic that as we get better and better at spreading the word and more communities learn how to better prevent, we'll see less and less heat-related illnesses."
Check out ABC News Senior Health and Medical Editor Dr. Richard Besser's tips for keeping cool for more information on ways that could save you and your family's lives.