Detailed Findings

The majority of these cities are located in the Southern states. Texas has the most cities on this list of hottest U.S. cities, with 16, followed by Florida with 8. Among the other hottest states in the country with numerous cities on our list are Louisiana and Mississippi.

Many of the hottest cities in America are also relatively dense and populous urban areas. As human-made creations such as buildings, roads, and other infrastructure replace natural landscapes, temperatures often rise. The result is what is referred to as a “heat island.” In the evening, the temperature in an urban heat island can be as much as 22 degrees warmer than in nearby rural areas. This excess heat can contribute to cities having increasingly unpleasant weather.

Methodology

To determine the hottest cities in America, 24/7 Wall St. ranked 192 cities based on the average number of 90-plus degree days per year, using climate data from the National Oceanic Atmospheric Administration’s 2018 Comparative Climatic Data report. In cases where multiple cities had the same amount of 90-plus degree days per year, the city with the higher average daily maximum temperature during its hottest month was given the higher rank. Only cities with populations of at least 10,000 were considered.

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 and 2010. The normal year round high temperature is the 30-year average daily maximum temperature from 1981 to 2010. Highest temperature on record refers to the highest temperature recorded at each city’s weather station, and this figure may differ from citywide or statewide figures. A full year’s data was not always available for the first year listed in each city’s range of recorded temperatures.