According to an article by John Metcalfe, Climate Central drew from the drew from the high emissions scenario in the Intergovernmental Panel on Climate Change's (IPCC) Fifth Assessment Report to elegantly map the year 2100 temperatures for 1,001 cities around the United States. Temperatures are expected to rise an average of 7-10 degrees Fahrenheit by 2100. This model assumes current greenhouse gas emission trends keep increasing through 2080 as they have been for the past several decades, according to Climate Central's report. In additional analyses, Climate Central used different emissions scenarios from the IPCC, and saw that U.S. cities will still experience varying levels of summer warming despite reductions.
The analysis looks primarily at daytime summer heat between July-August, as these temperatures are the hottest of they day. Moreover, the analysis precludes factors like humidity, wind, and dewpoint, which affect how insufferable summer heat can be.