The averaging period used for the following assessment was 1961-1990.
A dry month across virtually the whole UK, with Scotland having its driest September since 1972. Mean temperatures and sunshine were above average, with the exception of the far North of Scotland which had slightly below normal sunshine.
Driest September since 1959 at Dyce (Aberdeen) with 15.6 mm, and also the driest September at Plymouth since 1959, with only 4 mm of rainfall recorded. Swanage recorded 121 mm of rainfall on the 9th.
England and Wales diary of highlights
Dry and rather warm overall. Dry and sunny at first. Very wet at start of second week with torrential rain in places. Mainly rather warm, dry and anticyclonic.
1st to 4th A mainly dry and sunny start as high pressure drifted east to Russia, with a low forming over the North Sea by the 4th. It was generally rather warm with patchy mist and fog in places at first but there were outbreaks of rain in the south-west later.
5th to 9th Changeable to begin with as low pressure south of Iceland moved to the Irish Sea by the 7th. There were occasional outbreaks of rain and showers, especially in the west and north-west. Some heavy thundery rain affected Kent and Sussex overnight 6th/7th. A depression from Biscay on the 8th passed over the region during the 9th , bringing squally winds and depositing copious amounts of rain over a wide area. The rain was torrential in places causing flooding, especially in the north-west Midlands and the Swanage area - where 121 mm fell in 24-hrs, a one in 280-year event. Parts of the Isle of Wight were also deluged with up to 75 mm of rain in 24-hours.
10th to 20th Mostly dry under the influence of a ridge of high pressure stretching from an anticyclone over Scandinavia. The high centre later migrated to a position north then north-west of the UK. It was rather cloudy at times in eastern areas but there were often good sunny periods in central and western parts. Rather cool at times near the east coast but mostly rather warm or warm at times in remaining areas with Exeter reaching 26.5 °C on the 13th. Occasional spots of rain broke out over east coast counties and East Anglia from the 16th onwards. Some thundery rain affected south-west England at times during the 19th and 20th.
21st to 30th The high pressure continued to dominate the weather, later drifting south then eastwards into the continent. Though mainly dry with lengthy sunny spells there were some scattered light showers in places on the 22nd, and in the east on the 23rd and 24th as weak fronts gyrated round the high. Some showery rain also affected northern and eastern areas early on the 26th with thunder reported in East Anglia. Temperatures were mostly near normal, becoming rather warm at times especially after the 28th as a south-east airflow became established. The chillier night time spots had patchy mist and fog in the morning, with some districts having thick fog for a few hours. Some places experienced their first ground frosts of autumn. The last day saw showery outbreaks over Wales and south-west England, with a report of thunder in Cornwall.
Scotland diary of highlights
Anticyclonic and very dry.
The weather of September was dominated by anticyclones and hence was very dry. There was an unsettled spell from the 4th to the 10th, and this included one very wet day (the 9th). Apart from this, rainfall was scarce, although it was not always sunny.
September started with an anticyclone over England that moved steadily east to reach Denmark by the 3rd. Fronts pushed cloud south across Scotland on the 1st, but retreated north the next day. The bulk of Scotland experienced three fine days, with the temperature reaching 24.7 °C at Fyvie Castle in Aberdeenshire on the 2nd.
A steady fall of pressure introduced an unsettled spell from the 4th to the 10th as a depression moved south from Iceland to the English Channel. The weather was mostly showery, but the showers were heavy with flooding in Inverness on the 8th. The next day a front returned from the east to give a wet day, with 42.6 mm at West Freugh near Stranraer.
From the 11th to the 15th a large anticyclone over Scandinavia moved slowly southwest towards the Northern Isles. This gave a spell of warm and sunny weather to most parts, with the temperature reaching 25.6 °C at Lochcarron on the 12th.
The anticyclone became slow moving to the west of Scotland between the 15th and 20th. The change in the position of the High introduced cloud to many parts, with drizzle in the far north.
Colder, clearer air spread from the north on the 21st, with the anticyclone settling close to Scotland until the 24th. This brought a series of sunny days, but with cold nights. At Tulloch Bridge, the temperature fell to -2.5 °C on the 23rd and 24th.
Weak fronts crossed the country from the north and west on 25th and 26th, bringing cloud and some rain. High pressure became re-established on 27th and 28th, but the air was mild and rather cloudy. Southwesterly winds and weak fronts returned by the end of the month, but it remained warm with only a little rain.
Northern Ireland diary of highlights
Warm, Dry and Sunny This was the driest September month since 1996. The majority of Septembers' rainfall was recorded during the first 10 days and last day of the month. The period from 11th to 29th was fairly dry throughout the Province, however some western areas recorded some isolated and locally quite heavy showers on the 29th. It has been the sunniest September since 1997.
1st to 4th This was a rather warm and sunny period across the province. It was mainly dry though some scattered light showers occurred locally on the 3rd and 4th, however accumulations recorded would have been no more than one or two millimetres.
5th to 10th Low pressure prevailed bring rather unsettled conditions. Atlantic depressions and their associated weather fronts brought bands of rain and showers. Some heavy downpours occurred locally with between half an inch and an inch of rainfall being recorded on a number of occasions. Long sunny spells were recorded throughout the period.
11th to 14th High pressure dominated much of the weather during this period. It was warm and dry with some good sunny spells, except on the 12th, which was quite dull. One of the highest temperatures for the month was 21.8 °C which was recorded on the 11th in the Armagh area. Many areas also recorded maximum day-time temperatures of 20 °C on the 13th and 14th some 4 °C above the month average.
15th to 25th A dry settled period with little or no measurable rainfall measured anywhere. Daytime temperatures remained on the whole a degree or two above the average. Many areas recorded night-time temperatures in double figures between 15th and 19th. Slight ground frosts were recorded on up to four occasions in northern coastal areas while elsewhere they occurred locally on the 23rd and 24th. The dullest period of the month across Northern Ireland occurred between the 15th and 19th when virtually no sunshine was recorded anywhere apart from around one hour of sunshine on the 16th.
26th to 30th Early morning fog formed on the 26th and 27th which was locally dense in places. Temperatures were around or slightly above normal initially, though it became rather warm on the 29th, reaching 19 °C by the 30th in many locations. Between the 26th and 28th it was mainly dull, though some sunny spells were recorded on the 29th and 30th. Isolated light showers occurred on the 29th though these were locally quite heavy in the west of the province. The month of September ended with a band of moderate to heavy rain moving across the country from the south-west during the evening and late night of the 30th.