Last month was the warmest September in Armagh in a decade, the Observatory reported.
It was the third hottest since recording began in 1794. The mean temperature was 14.8 C.
It was also duller than average, with just 91 hours of strong sunshine, the least for eight years.
The warmest day was 23.1 C, which occurred on the 5th and the second warmest day was 23 C on the 6th.
These days were each followed by exceptionally warm nights, producing the two highest minimum daily temperatures for the month; 18 C on the night of the 5th/6th and 17 C on the night of the 6th/7th.
These two nights are now the second and sixth-warmest minimum September air temperatures recorded at Armagh since those records began at Armagh in August 1843.
The coldest day was 14.6 C, which occurred on the 30th. The coldest night (lowest minimum air temperature) was 5.4 C on the 22nd. There was one ground frost, also on the 22nd.