The Moyhu NCEP/NCAR index from the reanalysis data was up from 0.306°C to 0.368°C in September. That makes September warmer by a large margin (0.05°C) than anything in that index in recent years. It looked likely to be even warmer, but cooled off a bit at the end.
A similar rise in GISS would bring it to 0.87°C. Putting the NCEP index on the 1951-1980 base (using GISS) would make it 0.95°C. I'd expect something in between. GISS' hottest month anomaly was Jan 2007 at 0.97°C. Hottest September (GISS) was in 2014, at 0.90°C. It was the hottest month of 2014.
The global map shows something unusual - warmth in the US and Eastern Canada. And a huge warm patch in the E Pacific. Mostly cold in Antarctica and Australia, but very warm in E Europe up to the Urals, and in Middle East.
Weekly Climate and Energy News Roundup #260
3 hours ago