"The 1°F difference from 1998 is an unusually large margin, considering that annual temperature records are typically broken by just tenths of a degree Fahrenheit. In fact, the entire range between the coldest year on record, which occurred in 1917, and the previous record warm year of 1998 was just 4.2°F."...
"During the summer, nearly 100 million people experienced 10 or more days with temperatures greater than 100°F, which is about one-third of the nation’s population, NOAA reported.
With 34,008 daily high temperature records set or tied the year compared to just 6,664 daily record lows — a ratio of about five high temperature records for every one low temperature record — 2012 was no ordinary weather year in the U.S. It wasn’t just the high temperatures that set records, though. Overnight low temperatures were also extremely warm, and in a few cases the overnight low was so warm that it set a high temperature record, a rare feat."...
"According to data from NOAA's National Climatic Data Center, there were 356 all-time high temperature records set or tied across the entire U.S. in 2012, compared to four all-time low temperature records. All of the all-time record lows occurred in Hawaii."
So, yeah. Climate change, no climate change, who really knows, right? But if you're interested in seeing more about this topic, this video gives some more context.
(h/t Big Picture)