Graph: Extremely warm daytime high temperatures in the Southwest since 1910

The percent area in the U.S. southwest experiencing extremely warm daytime temperatures during the spring (top) and summer (bottom) months. The record dates back to 1910. The percent area experiencing extremely hot daytime high temperatures has increased in both spring and summer during the last two decades. NOAA Climate.gov graph, based on data from the National Centers for Environmental Information's Climate Extremes Index.