The averaging period used for the following assessment was 1961-1990.
Mean temperatures were exceptionally above average, with all district and regional climate areas having their warmest September (using areal series back to 1914). Driest conditions compared to average across SW England & S Wales, with Northern Ireland being one of the wettest areas compared to average. Sunshine above average across the majority of the UK, although well below average across Shetland.
England and Wales diary of highlights
An exceptionally warm month with above average sunshine.
1st to 3rd: Low pressure dominated the weather over the first 3 days of the month, with bands of rain and showers moving eastwards. Capel Curig (Gwynedd) recorded 20.2 mm on 1st and 47.2 mm on 2nd.
4th to 6th: A band of rain pushed northwards across the area during the 4th and 5th, although most of England and Wales remained cloudy on 5th. Patchy rain then moved back into northern England on 6th, fragmenting into a few showers as it pushed southwards through the day. Many areas had a fine and sunny day, with Margate (Kent) and Heathrow (London) both recording a temperature of 27.9 °C on 6th.
7th to 10th: A more settled spell of weather, with high pressure to the west of Ireland on 7th moving east over the North Sea by the 10th. Clear and sunny spells during this period, with overnight mist and fog in places, some dense fog in parts of eastern England on 10th. Very warm inland on 10th, with 27.8 °C being recorded in Central London.
11th to 14th: A warm and humid southerly flow, with many areas receiving heavy showers and thunderstorms. A fine sunny day in eastern England allowed temperatures to reach 30.2 °C at Heathrow (London) on 11th, the highest September temperature at Heathrow since 1949. Middle Wallop (Hampshire) recorded 32.6 mm on 13th, with many places in southern England registering 10-20 mm in just a couple of hours.
15th to 20th: A generally quiet spell of weather, with temperatures remaining above average and some fine and sunny days. A band of heavy rain pushed into western areas on the afternoon of 18th, but fragmented as it pushed eastwards through the evening and overnight.
21st to 30th: The final part of the month was unsettled and dominated by low pressure, but with temperatures still mainly above average. Remnants of hurricane Gordon late on 21st brought strong winds to the far west of the region, with 60 knots being record at St Mary's Airport (Scilly). However, most areas were very sunny and warm on 21st with Sutton Bonington (Notts) recording a high of 29.0 °C. Heavy showers and thunderstorms occurred in many areas during this period, with Wainfleet (Lincolnshire) recording 42.2 mm on 22nd, including a total of 21.8 mm in one hour. Flooding reported in Great Yarmouth (Norfolk) and Lowestoft (Suffolk) on 25th, with Lowestoft recording 52.9 mm in the 24 hour period ending 1800 UTC.
Scotland diary of highlights
It was the warmest September on record across Scotland and the whole of the UK. Southerly winds blew for much of the month, interrupted by a couple of spells with westerly winds..
Changeable westerly weather lasted for the first six days of September, with sunny periods and showers the main weather type. However, a secondary depression moving east across the Borders brought a wet day to the south on the 2nd, with 46 mm of rain at Dundrennan. Further rain, mostly in the south-west, occurred on the 5th in association with the next set of fronts.
A large anticyclone developed to the west of Ireland on the 7th and moved to the North Sea by the 10th. This brought a fine and sunny spell of weather to all parts. Nights were cold at first, with the temperature falling to freezing at Tulloch Bridge on the 8th. However, daytime temperatures rose steadily, reaching 24 °C at Lossiemouth on the 10th.
Warm southerly winds blew across Scotland from the 11th to 13th with the highest temperature (up to 24 °C) on the Moray coast. There were sunny periods, but also some outbreaks of rain. The weather broke down properly on the 14th as a front moved slowly across the country. Most places experienced a wet day with 38 mm of rain at Aviemore and 36 mm at Carterhouse.
Light southerly winds continued to blow across the British Isles between the 15th and 17th, with a mixture of clear and cloudy areas.
More vigorous changeable weather affected Scotland between the 18th and 22nd. Westerly winds gusted to 69 m.p.h. at Lerwick on the 19th and the 20th was a very wet day over much of the west with 41 mm of rain recorded at Broadford. Very warm air accompanied by clearing skies advanced north-west on the 21st, with the temperature rising to 25 °C at Edinburgh. Overnight a small but intense depression moved north and brought gales to the west coast, with gusts reaching 76 m.p.h. at Barra.
During the last week the main centre of low pressure remained in mid-Atlantic with mostly light southerly winds over Scotland. However, a small depression moving close to the west coast brought gusts of 74 m.p.h. to South Uist on the evening of the 27th. Apart from this, the general pattern of weather was of sunny periods and a few showers being interrupted by northward moving bands of rain.
Northern Ireland diary of highlights
Another record-breaking warm month in some areas.
The 1st to the 4th was an unsettled period with rain which was locally heavy at times in places on the 1st and persistent rain occurred again on the morning of Saturday the 2nd, giving 15 to 20 mm in places. Some bright or sunny spells did occur between the rain bands however and temperatures in the high teens were above the early September average.
The 5th to the 10th was a drier and warmer period everywhere with some sunny days, especially the weekend of the 9th and 10th when temperatures rose into the low-twenties. The maximum of 24.8 °C on the 5th at Killowen, was the highest maximum of the month.
Unsettled weather returned between the 11th and 15th with periods of rain which were locally heavy and thundery.
The 16th and 17th were fine and sunny days and temperatures reached 21 °C in many areas and up to 22.6 °C in the north-west. Some cool nights occurred, however, and as temperatures fell back well into single figures, some mist and patchy fog occurred at night. On the morning of the 16th, the temperature fell to 0 °C at Katesbridge (Co Down), the lowest value of the month.
The period between the 18th and 20th became progressively more unsettled again, culminating in a very wet day on the 20th and this continued overnight into the early hours of the 21st. By 9.00 a.m. on the morning of the 21st, 24-hour rainfall totals had reached 25 to 35 mm widely and up to 42 mm at St Angelo, Enniskillen in Co Fermanagh.
The early wet weather of the 21st cleared however to leave a drier, brighter and warmer day and in sunny interludes it became warm as temperatures rose to 20 or 21 °C. The late evening of the 21st brought easily the most dramatic weather of the month when a severe gale, the remnants of Hurricane Gordon swept northward across the area. Gusts 60 to 70 m.p.h. caused widespread tree damage and over 100,000 homes lost power. Quieter conditions returned on the 22nd though a few heavy, thundery showers affected western Counties in the afternoon.
The final week was dominated by low pressure and another ex-hurricane, this time Helene brought strong to gale force winds on the 27th together with further periods of heavy rain. Showery days followed for the close of the month and some showers were heavy, prolonged and thundery with Lough Fea collecting 30 mm of rain on the 30th during daylight hours.
This was a record breaking warm September in many areas and Belfast's mean monthly temperature of 14.7 °C beat the record of 14.5 °C which had stood since 1941. It makes it the second month in three to achieve new high, monthly mean temperature records.