September 2021 was the warmest September on record, according to the Armagh Observatory.
It recorded an average temperature of 15.5 degrees Celsius which is almost 3 degrees warmer than the long term average.
That average covers data recorded at the Observatory since around 1795, with temperatures recorded for more than 226 years.
It says temperatures in both August and September have increased significantly over the last 30 years.
Despite the warm weather, this September was the dullest for 38 years and it was wetter than average as well.