Up to two weeks of rain is expected to hit parts of the UK today, ahead of thundery showers across the country tomorrow.
Gale-force winds will also lash Britain, with gusts of up to 45 miles-per-hour set to batter parts of Scotland.
The Met Office said the rainy weather looks set to continue into the second week of October, meaning the country faces a three-week washout.
Greg Dewhurst, a Met Office forecaster, told Mirror Online: "From midnight last night to midnight tonight, some places in Scotland will get 40mm of rain.
"There could be 20mm in northern England and Wales. Since midnight we've had rainfall up to 15mm across north-west England and Wales.
"A band of rain is pushing east across UK. That band will clear during the early hours of this morning, although it may linger in some eastern parts.
"It's also going to be breezy, with the strongest gale-force gusts in Shetland and Orkney reaching 45 miles-per-hour.
"We could be facing rain for the next three weeks. There are signs it may become a bit drier and brighter towards the second week of October."
The Environment has issued seven flood alerts for today, in central, south-west and south England.
This means the following rivers could flood: the lower Avon, lower Soar, lower Tame, middle Tame, Anker, Sence, Trent and upper Tamar.
Tomorrow will be mostly dry with sunny spells in eastern England during the morning, while elsewhere it will be mostly cloudy with scattered potentially thundery showers.
Lightning is expected in Northern Ireland, all of Wales, north-west, west, central, south-west and south England tomorrow.
Through the afternoon there will be sunny intervals and heavy rain in some parts of the country, as well as a brisk south-westerly wind.
It will be unsettled with cloud and showers on Saturday, although the risk of thunderstorms will reduce.
Sunday will be overcast with heavy rain in England and Wales, while Scotland and Northern Ireland will be mostly dry with a few bright spells.
Met Office five-day weather forecast
Today:
Early rain clearing eastwards from most parts, followed by sunny spells and blustery showers; some heavy in the northwest. Windy for many; coastal gales in the far northeast.
Tonight:
Breezy with clear spells and occasional showers, some of these heavy in the north and west. Driest in the east.
Friday:
Sunny spells and showers, some heavy and thundery with some longer spells of rain too. Windy in the south with a risk of coastal gales.
Outlook for Saturday to Monday:
Remaining unsettled with sunshine and scattered showers on Saturday. A spell of heavy rain and strong winds across central and southern parts on Sunday; drier on Monday.
