The past year was the hottest on record for the 48 contiguous states in the US, the NOAA announced today, featuring the warmest spring ever, the second warmest summer, the fourth warmest winter, and an above-average autumn. Overall, the average temperature was 55.3 degrees F, or 3.2 degrees F above the 20th-century average. If that wasn't enough, it also the second-most extreme year on record, based on the US Climate Extremes Index, which takes into account factors like tropical storms, precipitation, and extreme temperatures.
The index came in at almost twice its average level, which makes sense given that 2012 saw 11 disasters that caused more than $1 billion in damage. Precipitation was significantly below average, as you might expect given the massive drought that hit much of the country this summer. The warmth also helped cause the drought; the lack of snow kept the soil dry, and the warm spring pushed up the growing season, draining what water there was from the soil faster.