Forecasters say the storm's transition from tropical to an extra-tropical feature makes it unpredicatable, but the effects are expected to deepen on Saturday night and leave a deliver a wet and tumultuous end to the weekend.
The Met Office said on Friday (August 8) there would be potential for rainfall totals of more than 50 mm in places and coastal gusts of over 60 mph, along with large waves. A spokesman added: "Given the unseasonable nature of the weather this could be sufficient to disrupt transport and make outdoor activities dangerous."
This will be particularly bad news for the Prudential RideLondon competitors, among them Sir Bradley Wiggins , who will be pedalling 100 miles through Surrey and London on the day.
For advice on coping with severe weather and the current forecast see the Met Office website .