Heat waves and maximum yearly temperatures in the U.S. have decreased over the last 100 years. SOURCE: Climate Science Special Report, Fourth National Climate Assessment | Volume I, U.S. Global Change Research Program, 2017 page 190 … the warmest daily temperature of the year increased in some parts of the West over the past century (Figure 6.3), but there were decreases in almost all locations east of the Rocky Mountains. In fact, all eastern regions experienced a net decrease (Table 6.2), most notably the Midwest (about 2.2°F [1.2°C]) and the Southeast (roughly 1.5°F [0.8°C]).
