This could be London’s wettest month on record, the Met Office has said.
The capital recorded 139mm of rain between the start of the month and October 25.
This is almost double the average of 78mm for the entire month.
October is usually the wettest month in the UK and rainfall this year has been largely concentrated in Greater London, the home counties in south-east England, and a smaller area of north-east Scotland.
With rainfall for the final six days of the month yet to be recorded, October 2020 is already ranking ninth rainiest in London since 1862.
Met Office spokesperson Grahame Madge said with “considerable rainfall” expected in the coming days it is “quite likely” this month will break the October record, and potentially that of any other month.
Mr Madge said: “The wettest calendar month on record was November 1940 with 171.2mm of rainfall.
“(Breaking this record) would require an extra 32mm of rainfall before the month end.
“On October 3 the UK received an average of 31.5mm on one day, so it is possible. However, we will have to wait before we can say for sure.”
That was the wettest day on record for the UK, with enough rain falling to more than fill Loch Ness.
The Saturday, which was just after Storm Alex hit, saw an average of 31.7mm across the nation, beating the previous record of 29.8mm on August 25, 1986.
Although Greater London and the home counties are experiencing a particularly wet October, rainfall around the UK has been only “slightly above average”, Mr Madge said.
“Virtually everywhere was wet on October 3, but since then there have been pockets of the UK which has seen higher rainfall totals, especially London and parts of the south-east,” he said.
“This is because of the way the jet stream has steered low-pressure systems more to the south of England.”
The UK’s wettest month of 2020 so far was February, when many regions were hit with devastating floods which destroyed homes and businesses.
Mr Madge added that climate change is having a “pronounced effect” on temperatures in the UK, raising averages by about 1C (1.8F) since pre-industrial times, and the warmer atmosphere could be causing increased rainfall too.
He added that UK climate projections show warmer, wetter winters and hotter, drier summers will lead to “more extreme rainfall records” by the end of the century.
Hertfordshire is also seeing its ninth wettest October since 1862, with Bedfordshire, Berkshire, Buckinghamshire and Oxfordshire experiencing their tenth soggiest.
In north-east Scotland, this month is the third wettest for Moray, fourth for Banffshire, sixth for Kincardineshire, seventh for Aberdeenshire, and ninth for Nairn and Angus.