Heatwaves: "Longer-term records show that heat waves in the 1930s remain the most severe in recorded U.S. history..."

"6. Longer-term records show that heat waves in the 1930s remain the most severe in recorded U.S. history (see Figure 3). The spike in Figure 3 reflects extreme, persistent heat waves in the Great Plains region during a period known as the 'Dust Bowl.' Poor land use practices and many years of intense drought contributed to these heat waves by depleting soil moisture and reducing the moderating effects of evaporation."

~ from the US Environmental Protection Agency website, cited in Calvin Beisner's article 'Are This Summer's Heatwaves Extraordinary?'