UK weather: Exact date most of Britain facing deluge as sunny spell ends

New weather maps have revealed the exact date the latest sunny spell is set to end, with a massive rainy deluge set to dump more than an inch of rain on the UK.

Conditions over the last week have become hugely unpredictable for vast swathes of the country, with heavy rain prompting Met Office weather warnings and the mercury dropping down below 20C during the day for the first time in weeks. Forecasters have previously warned that September would likely prove unpredictable, and this will be the case in the next few days.

The latest maps from WXCharts show an en route deluge that could drench Brits living across hundreds of miles in more than an inch of rainfall over just a few hours.

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Maps from the service - which uses data from MetDesk - show a massive rainy system wheeling towards the UK from the west running on a collision course with the country by the morning on Wednesday, September 13. The first patter of rain will commence from around 6am, scattered along the west coast at Scotland, hitting Galloway Forest Park, most of the Outer Hebrides, and the far northeast coast around Achmelvich.

By 9am showers will move further east inland, still sticking in Scotland, with one wet patch on the south coast near the Isle of Wight. At most, the earliest showers will create around 0.6mm of rain per hour, with the intensity kicking up by 3pm, with 3mm per hour hitting Wales and Scotland first.

By 6pm, the showers will have moved on to cover England, Scotland and Wales, with the worst rain south of the border descending on Birmingham and Manchester. Further north, the heaviest rain appears likely to fall on the Yorkshire Dales National Park and North Pennines National Landscape.

In Scotland, the most severe showers seem likely to hit Edinburgh, with the overall rain system pelting the country until it drifts off the east coast at 9pm. Overall, 5mm of rain falling per hour between 3pm and 9pm means the country will see up to 30mm in total on September 13, around 1.18 inches.

At its peak, the The Met Office long-range forecast suggests that the unsettled weather on Wednesday will persist over the rest of the week, with "heavy rain or showers" on the cards alongside "spells of strong winds". The forecast states: "This period is likely to start out unsettled, with low pressure dominating the pattern.

"This will mean showers or longer spells of rain will affect most of the UK at times. Some heavy rain or showers are expected in places, most often in the west and north. Thunderstorms and hail are also possible, as are some spells of strong winds, especially if any deep areas of low pressure develop and affect the UK.

"Later in the period, there may be some longer spells of drier weather that develop, especially towards the south, with more in the way of sunshine due to higher pressure. Temperatures will likely be close to average or slightly below overall, but may rise above at times in any drier, sunnier spells."