When summer sweat becomes too much to handle, the demand for a chilly escape route rises. That's when Bert Sperling, the owner of bestplaces.net, and his list of the top 50 "chill" and "sizzling" cities steps in, happy to offer guidance.
Using the Sperling Heat Index -- a formula the author created that combines daily high temperatures, dew point and nighttime low temperatures -- the site's specialists analyzed 30 years of June and July weather reports starting in 1980 through 2010 to determine the coolest and hottest metropolitan cities in the USA.
"This is a great list for people who are looking to relocate or just looking for a vacation," he says, explaining the goal is to find places that have comfortable and safe summers. The mission began after he created "Places, USA" software, which collects data from travelers helping the site's staff find the best places to travel, live, work or retire.
Seattle was the chilliest or most comfortable summer city, with an average daytime temperature of 74.9 degrees, a nighttime low of 52.9 degrees and a dew point of 50.8 degrees. Portland, Ore., San Francisco, Denver and San Jose, Calif., were also listed in the top five chill summer cities.
"I don't have too much of an issue with these rankings," says Brett Anderson, a senior meteorologist at AccuWeather. "Others may (disagree), but a majority wouldn't complain."
The meteorologist says cooler places are more common in the Pacific Northwest or near the West Coast because of the cool ocean breeze and current. Midland regions tend to be hotter because of the lack of elements, like an ocean breeze, to provide relief. Southern regions are also less preferable because of high temperatures and levels of relative humidity, sometimes providing little chance for the body to recover.
"The Pacific Northwest has the most perfect summers imaginable," Sperling says.
In combination with weather data, specialists also looked at heat-related mortality rates reported by the CDC and National Weather Service, finding states with the highest amount of heat-related deaths included Missouri and Illinois.
Despite the comfortable climate and low health risk, none of the top 10 chill cities were ranked among the most visited destinations in the USA, according to a Forbes report in 2010. Forbes' top visited cities are also some of the hottest, according to Sperling's report, including Miami, Las Vegas and Dallas, where temperatures can reach into the 100s and high 90s with little relief.
"You want to avoid the places with high heat index," Sperling says. "Places with a low heat index are the places where chances are pretty great that you'll have a nice cool experience."
Top 10 Chill Cities:
2. Portland, Ore.
3. San Francisco
5. San Jose, Calif.
7. Salk Lake City
Top 10 Hottest Cities:
2. Las Vegas
6. San Antonio
8. New Orleans