Updated 26th September
Covering the period 3rd October - 25th October
Warm and changeable until early October, then dry, with variable amounts of cloud, but some regions notably sunny
Consistent but unexceptional warmth will be a regular theme, with mean temperatures coming out between 1 and 1.5C above the 1981-2010 average for much of the country.
Rainfall totals will be below normal in most parts of the country, especially over England and Wales, but much of Scotland and Northern Ireland will see significant rainfall in the first week, resulting in only slightly below average rainfall for most places.
Sunshine totals will be slightly below normal in south Wales and south-west England, but rather above normal in most parts of Scotland and northern England, and near normal elsewhere.
Monday 3rd October - Sunday 9th October
Changeable west to south-westerlies will dominate during this week but with a growing tendency for high pressure to ridge into the east and south, keeping weather systems more confined to north-western Britain.
Strong south to south-westerly winds will dominate over the British Isles between the 3rd and 5th. It will be cloudy and wet for most of the country on the 3rd, though with only small rainfall amounts for the south, due to a large area of high pressure over Europe influencing the weather in the south-east in particular. It will be warm in eastern England with maximum temperatures locally hitting 20 or 21C. The 4th will be a brighter showery day in between the rain belts, with most of the showers in the west. The 5th will be another cloudy, warm and humid day, with some large orographic rainfall totals likely over the higher ground of south-west Scotland.
Between the 6th and 9th, however, the Euro high will influence Britain's weather far more strongly, with the high often ridging into the south of the British Isles. Rainfall amounts will consequently be low over most of the country, though still with some active rain belts for north-west Scotland. However, it won't be a consistently sunny and dry anticyclonic period because weak Atlantic frontal systems will frequently move around the northern periphery of the high pressure, bringing areas of cloud and patchy light rain or drizzle from west to east. In between the rain belts there will be a fair amount of sunshine, especially in any polar maritime north-westerly incursions. Thus sunshine will tend to be variable rather than plentiful, but overall coming out above average for much of central and southern Britain during the second half of the week.
Overall, mean temperatures will be between 1 and 2C above the 1981-2010 average over much of the country. Some colder incursions into the north will result in an anomaly close to 1C over much of Scotland and Northern Ireland, but over much of England and Wales the anomaly will generally be nearer 2C.
Rainfall totals will be close to or above normal in the west (except for south-west England and south Wales, where it will be a little drier than average) and generally below normal to the east of high ground and in central and southern parts of England. Rainfall totals will tend to be significantly above normal in upland parts of western and central Scotland.
Sunshine totals will mostly be near normal for the week, with a dull start and a sunnier end, but it will be cloudier than average in some western areas.
Monday 10th October - Sunday 16th October
This week will be predominantly anticyclonic with southerly winds blowing more frequently than usual, although there is some uncertainty over exactly where the high pressure will end up. Thus, most of the UK will be drier than average, and there will be some chilly and misty nights at times, but it will tend to be warmer than average by day. Mean temperatures will again mostly be between 1 and 2C above the 1981-2010 average, but generally less warm relative to average in central and southern Britain than the previous week, with an anomaly nearer 1C.
Rainfall totals will be below normal everywhere, with some particularly significant shortages in north-western Britain due to the relative lack of westerlies coming in off the North Atlantic. Sunshine totals will mostly be above normal but with considerable local and regional variation due to the possibility of stubborn banks of cloud being slow to clear at times. In general, Scotland and north-west England will tend to be sunniest relative to normal, with the south of Britain more likely to have close to average sunshine.
Rest of the month
Monday 17th October - Tuesday 25th October
The early part of this period is expected to remain quiet and anticyclonic, with temperatures generally falling close to the long-term average. Most regions, especially the west, will tend to be sunnier and much drier than average. However, later in the period, cloudier and warmer weather will push in from the west, bringing rain at times also, especially to the west, and winds will be predominantly south to south-westerly with high pressure holding on for a while in the east. Overall, the period will be about 1C warmer than average, with rainfall totals rising close to normal in south-western Britain and Northern Ireland, but generally below normal elsewhere, particularly in eastern and northern Scotland. Sunshine totals will mostly be near or a little above normal.