It was the warmest September for between six and 11 years in much of Ireland and the warmest since 1971 at Malin Head, Co Donegal, according to Met Éireann.
The first half of the month was very warm, with both day and night temperatures about three degrees higher than normal for the period.
However, sunshine totals for the month were a little below normal at almost all weather stations, and despite a very sunny first week it was the dullest September for between five and eight years.
Rainfall totals were above normal in coastal counties in the west and south. However it was a relatively dry month generally, with approximately three-quarters of the normal September rainfall recorded in parts of the east and midlands.
The number of wet days in September varied widely from 10 in the Dublin area to 21 at the Valentia observatory.
The highest temperature reached 24.5 degrees in Belmullet, Co Mayo, on September 4th. The lowest air temperature was recorded at 0.1 degrees at Mullingar, Co Westmeath, on September 24th.
There were between three and five ground frosts recorded at inland stations during the second half of the month, with air temperatures falling close to freezing on September 24th.
Many stations measured their lowest September air and ground temperature for between 10 and 20 years on that day.
Average wind speeds were between seven and 13 knots. After relatively light winds during the first half of the month, they were much stronger during the second half, with the highest gusts measured at 51 knots at Belmullet on September 26th and 30th.
Thunder was only recorded on September 4th, 5th and 26th.
Fog was most frequent on September 5th, 6th and 26th.