By: Bob Henson , 6:10 PM GMT on December 07, 2016
The autumn of 2016 was the warmest ever observed in records going back to 1895 for the 48 contiguous U.S. states, according to data released on Wednesday by NOAA’s National Centers for Environmental Information (NCEI). The nation’s average September-to-November temperature of 57.63°F was a full 1.05°F above the previous autumn record, set way back in 1963, and it was 4.08°F above the 20th-century average (see Figure 1). The record-setting margin of more than 1°F is a hefty one for a temperature record that spans an entire season and a landmass as large as the 48 contiguous states. For comparison, the second, third, fourth, fifth, sixth, and seventh-warmest U.S. autumns are all clustered within 1°F of each other, as are the six coldest autumns on record.
Pushing this past autumn to the top of the temperature pack were the third-warmest October and third-warmest November on record, along with the ninth-warmest September. Eight states along a swath from New Mexico to Michigan saw their warmest autumn on record, and every contiguous state except for California, Nevada, Oregon, and Washington had a top-ten warmest autumn
Although it wasn’t the warmest November on record, last month transcended all other months in modern U.S. weather history by the outsized presence of record highs to record lows. According to preliminary NOAA data compiled through Wednesday, November saw 4544 daily record highs set or tied, and just 94 daily record lows set or tied--a ratio of more than 48 to 1! This is the largest such ratio for any month in U.S. data going back to the 1920s, according to independent meteorologist Guy Walton (@climateguyw), who has tracked U.S. records for many years. Because many U.S. reporting stations came on line in the 1890s, the occurrence of records did not stabilize until around the 1920s.
Although 2016 is running just behind 2012 as the warmest year in U.S. records thus far, the widespread chill expected to continue through at least mid-December has a good chance of keeping this year from outpacing 2012.