Scattered showers will turn to heavy rain later today.
Further showers will then follow and it will also become windy with a risk of gales.
Showers and heavy rain will continue tonight with gales becoming more widespread.
Several flood warnings are in place, mainly in the south, but disruption on the rail network is expected to be widespread.
Passengers on Grand Central Trains from Halifax to Kings Cross can expect delays.
As a precautionary measure, Network Rail, which is responsible for the track and other infrastructure of the railway, has imposed a 50 mph speed restriction for services on the line between London King’s Cross and Peterborough this afternoon.
Forecasters indicate the severe weather will continue until the early hours of Christmas Eve in the London area, and this may have an additional knock-on effect to services on Christmas Eve, whilst Network Rail carries out safety checks to the track and other infrastructure.