Updated 29th September
Covering the period 6th October - 28th October
A warm start to the period, then turning cooler. Generally drier than average until the last week of October, then turning wet
Rainfall totals are expected to be slightly below average in most parts of the country in spite of a wet end to the period, and significantly below average in the north and west of Scotland, but in general the trend is towards less settled conditions than we have been used to during September.
Temperatures will come out 1 to 2C above the 1981-2010 average in eastern parts of England, and generally less than 1C above elsewhere, with northern and western Scotland and Northern Ireland generally within 0.5C of the normal.
Sunshine totals are expected to be near normal in most parts of the country, but it will generally be sunnier than average in the north and east of Scotland.
Monday Monday 6th October - Sunday 12th October
A slow-moving low pressure system will become established to the west of the British Isles during this period, though with some uncertainty over how far west the low will end up. Meanwhile, pressure will remain high over central parts of Europe and this will result in mainly southerly winds across the British Isles. The low pressure will be strongest early in the period, when it will bring some belts of rain eastwards through the British Isles, heaviest in western parts of the country, with only small rainfall amounts likely in eastern parts of England and Scotland. Eastern parts of the country are likely to be significantly warmer than average due to southerly winds, and temperatures in south-east England will sometimes exceed 20C. Western parts of Britain will have near or slightly above average temperatures.
During the second half of the period, the low pressure is expected to slacken and high pressure will tend to build from both the north and the south, with highest pressure centred to the south-east of the country. This will result in generally quieter weather, with rainfall below average, and temperatures close to or slightly above the seasonal norm.
Overall, temperatures will be up to a degree above the 1981-2010 average during this period in western parts of the country but may be 2 to 3C above in eastern parts of the country, with central parts 1 to 2C above. Rainfall totals are likely to be above the seasonal norm in Northern Ireland, Wales and western England, but below average in the north and east of Scotland and in eastern England. Sunshine totals will generally be close to or slightly below the seasonal norm in western parts of the UK but the east of Scotland and England will generally be sunnier than average.
Monday 13th October - Sunday 19th October
High pressure will tend to be the dominant influence on the weather during this period, but there will be an increasing tendency for the high to be centred to the west of the country, and with rising pressure around Greenland and Iceland, increasing the chances of cold northerly winds affecting the country late in the period, especially in northern and eastern Britain.
Rainfall totals will be below the seasonal average everywhere, with western parts of the country likely to see the largest rainfall shortages during this period. Temperatures are expected to fall close to or slightly below the seasonal average, with Scotland and Northern Ireland most likely to fall slightly below the average, being the most prone to cold nights and imports of cold arctic air from the north late in the period. Sunshine totals will generally be close to average, but western Scotland and Northern Ireland are likely to be sunnier than average during this period.
Rest of the month
Monday 20th October - Tuesday 28th October
The weather is likely to turn somewhat more unsettled during this period, with cold northerly winds likely at the start of the period and then low pressure dominant towards the end of October, as pressure falls to the north of the British Isles. Consequently, I expect rainfall totals to rise above the seasonal norm in most parts of the country, with the south of Britain most likely to see significantly above average rainfall, and Scotland likely to be closest to average, as the jet stream is likely to lie to the south of its usual position.
Sunshine amounts are likely to be below average in most parts of the country but in Scotland and Northern Ireland they may be near or slightly above average, especially in northern Scotland. Temperatures will generally be close to average over England and Wales, but are more likely to be below average over Scotland and Northern Ireland.