19 October 2016
It was by a razor thin margin over 2015, but this September was the hottest on record based on NASA GISS data. NOAA does a separate analysis and puts it as number two after last Sept. NOAA did report that the land temps. in Sept. were the hottest on record, beating last year.
Here is the stunning statistic:
September 2016 was the 381st consecutive month with above average global temperatures.
Check out the warming below since 1880 in this excellent info gif from NASA: