Met Office pinpoints exact timeframe 100mm of rain will batter parts of UK

More than one month's rain will lash across parts of the UK in around nine hours - and flooding is feared.

A band of low pressure will sweep east across the weekend, leading to the deluge throughout Saturday. The Met Office, which has two weather warnings in place for rain, has now identified the timeframe, during which up to 100mm (nearly four inches) will fall in some areas.

Even after this period, Brits should be alert and continue to prepare for flooding, as further showers are forecast for Sunday. There are 15 flood warnings and alerts in place, all for Cumbria, in and around the Lakje District National Park.

The Met Office's website reads: "Rainfall will spread northeastwards on Saturday, and become persistent and at times heavy. Through this period 20-40 mm of rain is expected to fall widely, with some locations perhaps seeing 75-100 mm, with much of this total falling in the later hours of the event." The event, to which the Met Office refers, is the weather warning in place from 9am tomorrow until 6pm.

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The weather warnings concern parts of County Antrim and County Down in Northern Ireland, and most of western Wales and northern England. Weather maps, issued by a different forecaster called Metdesk, show the heaviest of the rain is expected across north Wales, Merseyside, Greater Manchester and Lancashire during lunchtime.

And then there will be huge downpours further east - notably across Humberside - later in the afternoon. Higher ground in any of these areas could see the 100mm peaks fall across the nine hours altogether. Typically, most cities across northern England - including Liverpool, Manchester and Hull - see between 60mm and 80mm of rain fall in an average September. Even across Scotland, only the Inner and Outer Hebrides tend to experience more than 100mm of rainfall in a standard September.

The Met Office's website adds: "From mid-Saturday onwards, increasingly strong gusty winds and perhaps some thunder will also accompany the rainfall, further increasing the risk of disruption... There is a small chance that heavy rainfall may cause some transport disruption and flooding.

"There is a slight chance of power cuts and loss of other services to some homes and businesses. There is a small chance that homes and businesses could be flooded, causing damage to some buildings. Where flooding occurs, there is a slight chance of delays or cancellations to train and bus services.

"Spray and flooding could lead to difficult driving conditions and some road closures. There is a small chance of fast flowing or deep floodwater causing danger to life."