Methodology

To identify the hottest cities in America, 24/7 Wall St. reviewed the average number of days each year that temperatures of 90°F or higher are recorded in 254 U.S. cities. Figures came from the National Oceanic and Atmospheric Administration’s 2015 Comparative Climatic Data report. Averages for each city were calculated over varying periods, depending on when the city began keeping records.

The normal mid-summer high temperature is the 30-year average daily maximum temperature from the month with the highest average daily temperature for each city using data recorded between 1981-2010. Mid-summer afternoon humidity is the average relative afternoon humidity for the same month as the normal mid-summer high. Highest temperature on record refers to the highest temperature recorded at each city’s weather station and may differ from citywide or statewide figures.