AOL Weather - latest forecasts
Autumn officially begins tomorrow according to astronomers - and it kicks off to a typically mixed start with Britain set to be hit by rain, fog and sunshine.
Bookies have slashed the odds on this year being the wettest ever as much of the country is battered by heavy downpours today.
More rain is forecast for tomorrow, but weather experts said the south will enjoy spells of sunshine, while temperatures will warm up towards the end of the week.
Laura Young, from the Met Office, said this mixed bag of weather is typical for autumn.
She said: "As with any seasons there is a transitional phase. You don't hit December 1 and it becomes immediately freezing cold. You are more likely to see snow at the end of winter than the beginning.
"Certainly it can be quite settled but it can also be quite volatile in September, it all depends.
"We have had a mixture of wet and windy and very warm and dry. We have had a good mixture which is fairly typical for September."
While weather experts say the season starts on September 1, astronomers take their cue from celestial events and say it begins on the Autumn equinox, when the length of day and night are equal. This hits tomorrow.
Much of Britain will wake up to a chilly and bright start tomorrow, but cloud and rain will hit Scotland and Northern Ireland in the morning and sweep across much of England and Wales.
On Thursday parts of the north are expected to be hit by thundery showers and stronger gusts of wind, while the south will be clearer with some light showers.
But Ms Young said the weather will warm up on Friday with temperatures hitting around 18C (64F) in the south and creeping up to around 20C (68F) on Sunday.
She said: "There is quite a lot of sunshine around on the weekend, particularly on Saturday.
"It will mainly be staying dry and that will hang around until the middle of next week. That could bring mist and fog overnight."
She said Britain is set to see "warm days and chilly nights because we are going into that autumn weather".
Meanwhile Ladbrokes say it is odds-on that 2015 will be declared the wettest on record.
The bookies say there is a 6/5 chance this year goes down in history as the wettest yet, while they are offering 4/1 that this September will notch up the same accolade.
Alex Donohue of Ladbrokes said: "As every drop of rain falls the odds follow suit, and it's now looking increasingly likely that 2015 will be chalked up in the history books as the wettest year we've ever seen."