September 2021 was the second warmest on record for the UK.
The mean temperature of 14.7C for the UK was only slightly cooler than the 15C figure which was recorded in August, according to provisional Met Office figures.
The UK’s warmest September was in 2006 when the temperature reached 15.2C, the Met Office said.
Dr Mark McCarthy, head of the Met Office’s National Climate Information Centre, described September 2021 as being “an exceptionally warm month for the UK” in which there were “persistent above-average temperatures” until the conditions changed right at the end of the month.
Warm nights helped Northern Ireland to its joint-warmest September on record, with mean temperatures of 14.2C, which matched those recorded in 2006.
The highest average minimum temperature in Northern Ireland in September was a record figure of 10.7C, topping the 10.5C reached in 2006.
The Met Office said that September 2021, which came on the back of a more subdued August, saw the UK as a whole enjoy its second warmest September based on figures dating back to 1884.
Dr McCarthy said: “Interestingly, the exceptionally warm start of the month at one time threatened to push September’s average temperature figures above August’s, but the recent unsettled weather and drop to more average conditions have driven the figures slightly below August’s, but still well above the long-term average.
“High pressure dominated for much of the early part of the month, which brought with it warm, sunny spells and calm conditions.
“Although that particularly warm heat subsided, the temperature remained above average for a good portion of the month, before a more unsettled breakdown late in the month and more low-pressure systems moving in to the UK.
Glasgow which is hosting the Cop26 climate change talks in November, recorded its joint hottest September with a temperature of 14.9C, matching the top figure dating from 2006, the Met Office said.
Despite last month being Northern Ireland’s joint warmest, it was also a particularly dull time as the hours of sunshine were the lowest since 1965.
There was an average of just 74.3 hours. The dullest September figures were set in 1962 when just 73.6 hours of sunshine were recorded, the Met Office said.
Temperatures of more than 30C were recorded in some places early in September. Wales topped 30C in September for the first time since 1961, when Dyfed was basking in similar temperatures on September 7.
This was still shy of the all-time September temperature record in Wales of 32.3C set at Hawarden Bridge on September 1 1906.
Other hot days included September 7 and 8 when 27.2C was recorded in Plymouth 27.1C in Eskdalemuir and 25.8C in Balmoral.
September 2021 was second warmest on record for the UK, with Northern Ireland having its joint warmest September on record. Read more about our stats for September in our news release https://t.co/cbWoRXbG74
— Met Office (@metoffice) October 1, 2021
The Met Office said that despite the heat slipping slightly, temperatures remained above average for a good portion of the month, before shifting to the more typical autumnal weather and bouts of persistent rainfall in the last week of September.
Rain late in the month for much of the UK brought the average rainfall figure to 78.8mm, but this is still just 82% of the average rainfall for September.
Western areas saw more of the rain, especially in Northern Ireland and Wales, but even in these areas, rainfall was slightly below average. Drier conditions were found in northern England and some parts of the south-east, according to the Met Office.