The averaging period used for the following assessment was 1961-1990.
Sunshine was close to average across western areas, and well above average over most eastern areas of the UK. Rainfall was above average across many western parts, however south-west England along with most southern and eastern areas, had below normal rainfall. Mean temperatures generally one or two degrees Celsius above average.
Dyce (Aberdeen Airport) experienced its sunniest September since records began in 1946. Wisley (Surrey) recorded a temperature of 29.2 °C on 5th.
England and Wales diary of highlights
Generally fine, settled and very warm conditions at first but more changeable weather was experienced from the 10th with showers of longer spells of rain. Despite this, and rather windy conditions at times, rainfall was below average and it remained rather warm across most parts.
1st to 5th: Fine weather was predominant through this period with most parts largely dry and reasonably sunny. It was also warm or very warm across most parts and locally hot. On the 5th Cardiff reached 28.6 °C, their warmest September day since records began in 1895. On the same day Wisley in Surrey recorded 29.2 °C. The exception to the sunny weather was western coasts and hills which were affected by low cloud and occasionally drizzle. Mist, low cloud and patchy fog affected other parts by night.
6th to 9th: Although still warm and sunny in the south on the 6th, it was dull and cloudy across northern England and Wales as far south as The Wash and overnight the cloudy conditions and patchy drizzle extended south. Bright or sunny spells developed on each of the following few days only for low cloud, mist and fog to reform overnight. With the exception of some patchy drizzle (mainly overnight) most parts remained largely dry. However, thundery showers developed across Cornwall on the evening of the 9th, heralding a more unsettled spell of weather.
10th to 14th: This period saw more unsettled conditions across England and Wales. The 10th was rather cloudy across most parts. Heavy rain, thundery in places, affected Wales and more southern counties during the morning. Despite the rather cloudy skies it was generally warm and locally very warm in the north and east with Keswick reaching 23.3 °C. A mixture of clear/sunny spells and showers affected most parts over the following days with occasionally more persistent bands of rain sweeping across. The rainfall was particularly heavy across the Welsh mountains on the 12th with 41.4 mm recorded at Capel Curig (09-21 GMT). It was also rather windy through this period with gusts of 55 knots at Aberdaron and the Mumbles on the 12th, 54 knots and 64 knots at the Mumbles on the 13th and 14th respectively.
15th to 16th: A brief respite occurred during this period with, apart from a few showers across East Anglia and the south-east, many parts dry with clear/sunny spells. Clear spells overnight on the 15th allowed an air frost to develop at Redhill airfield. Later on the 16th further rain pushed across more western parts, an indication of more unsettled weather to come.
17th to 24th: It was rather cloudy through the 17th and 18th with outbreaks of rain and drizzle and some heavier pulses of rain pushed south-eastwards on the 18th. Showers were a feature of the weather from the 19th to the 24th and although some bands pushed eastwards, western parts bore the brunt. Capel Curig recorded 58 mm during the 24 hour period beginning 18 GMT on the 19th. It was also windy from the 18th to 23rd with gusts of 55 knots across northern England on the 20th. Despite the unsettled weather it remained rather warm in the south with Wisley recording 21.9 °C on the 23rd.
25th to 30th: With the exception of the 26th, when it was largely dry with clear or sunny spells, skies were generally rather cloudy through the rest of this period. Weather fronts brought bands of rain across and thundery showers developed on one such weather front across Lincolnshire and Norfolk on the evening of the 28th. Thundery showers also developed across East Anglia and Lincolnshire on the 30th as another weather front cleared eastwards.
Scotland diary of highlights
September was unsettled with changeable westerly weather types dominating the month. However, there was a notable anticyclonic spell with fine and sunny weather between the 7th and 9th. The combination of this and the prevailing westerly flow meant that Dyce experienced its sunniest September since records began in 1946.
September began with a mild south-westerly airflow bringing much cloud with occasional showers or spells of light rain. Very warm and humid air reached Scotland on the 4th, maintaining the cloud with some drizzle in the west. In the east the cloud broke to allow the temperature to reach 25 °C at Dyce and the overnight minimum at Edinburgh was 17 °C.
An anticyclone built across Scotland on the 5th and moved slowly east over the next few days. Cool and clear air reached the north but a weak front maintained cloudy conditions in the south. The clear air spread south on the 6th and all parts enjoyed sunny weather for the next three days. Daytime temperatures gradually rose so that on the 9th at Glenlivet it ranged between freezing and 26 °C.
From the 10th to the 13th an area of low pressure to the north-west of Scotland dominated the weather. It was mostly showery but the showers were heavy at times and accompanied by spells of strong wind. During these four days there was 120 mm of rain at Dalmally and 116 mm at Tyndrum.
On the 14th the winds veered into the north-west and a ridge of high pressure gave a sunny day on the 15th.
Boisterous conditions returned between the 16th and 21st with the main area of low pressure near Iceland. The wettest spell was on the 19th and 20th when over 100 mm of rain fell at Dalmally, Tyndrum and Sloy. Gusts of wind approached or exceeded 60 m.p.h. at one or more stations on several days.
On the 22nd the low transferred to Scandinavia, the weather quietened down somewhat and on the 24th a ridge of high pressure gave a fine day in most places.
Generally unsettled westerly weather returned for the remainder of September. There was more wind on the 26th as another depression moved east near the Faeroes, with gusts of up to 76 m.p.h. at Sella Ness. A final batch of rain crossed the country on the 29th/30th, with 35 mm at Tiree.
Northern Ireland diary of highlights
Mostly fine and warm at first, then changeable.
The 1st to 9th was a fine period in all areas, with some warm sunshine on most days. The period between 7th and the 9th was particularly sunny with almost unbroken sunshine in some parts. Temperatures were frequently into the low 20s °C and a high of 24 °C was recorded at Helens Bay and Newry on Saturday 4th - the months highest values.
The weather changed abruptly on the 10th when a band of rain gave many places a wet day. A total of 25 mm of rain was recorded at Glenanne in Co Down. This heralded the arrival of much more autumnal weather. It became windy with showers or some longer spells or rain for much of the next two weeks and temperatures struggled at 13 to 15 °C by day, though nights remained mild. Winds reached gale force at times, with the 20th a particularly windy day everywhere, with gusts to 55 m.p.h. over some exposed parts of the Down coast.
A brief respite occurred around the last weekend of the month and although some light rain occurred at times, the period between the 24th and the 27th was warmer with temperatures returning to above normal, with values of 18 to 20 °C.
The 28th to 30th saw a return to unsettled weather and an active cold front brought heavy rain to all areas overnight on the 29/30th, 15 to 20 mm was recorded widely and locally 25 mm or more.
Overall, rainfall was around average with distinct peaks around the 10th, 19th, 20th and again overnight on the 29th/30th.