Heavy rain is predicted to fall across the southeast of England throughout the day and motorists are advised to take care on the roads which may be affected by localised flooding.
Forecaster Hannah Findley, of The Weather Channel, said: "A complex area of fronts in north-western Europe will bring cloud and rain to France and southern Britain".
The south east will bear the brunt of the onslaught with one and a half inches of rain likely in a few hours, according to the Met Office.
The Environment Agency is expecting the river Leen in Nottinghamshire to flood, while areas around the North Sea coast at Scarborough have been put on alert.
"In addition, flooding of homes and businesses is possible".
In their south west summary, Met Office said: "A cloudy and cool day with heavy showers or longer spells of rain for most areas". Where these occur they are likely to be slow moving and perhaps thundery.
A total of three inches would top the average rainfall for the whole of August in many places.
Roads and railways are expected to be disrupted by the downpours.
The rain will turn heavy and persistent at times, particularly during the early hours.
"The extent of the flooding and travel delays will vary greatly across the region; however, significant impacts are possible in locations that receive repeated heavy downpours".