Temperatures rose in each of the continental 48 states since 1970.
In the United States, the first five months of 2012 have been the warmest on record. More than 100 cities out of 150 recorded have seen their warmest recorded temperatures.
Just a quick glance at this chart gives a good insight into how steamy our cities have been so far this year. But while this year is off-the charts it's not a surprise. We've seen temperatures on the rise for decades, as a new report from Climate Central illustrates.