A spokesman said scattered showers are likely to develop this morning and become locally heavy and thundery by the afternoon.
"The public should be aware of the risk of localised surface water flooding. "
The showers should gradually die out from the west this evening .
The chief forecaster said: "A deeply unstable airmass will cover much of eastern and central England today. As daytime heating gets going, showers are likely to develop quite quickly during the late morning and become heavy and thundery in the afternoon.
"The showers may become organised into narrow slow-moving bands, with some places having over 15 mm of rain in an hour and up to 30 mm in 2 or 3 hours. As often happens in such situations, some places will escape the downpours. "
Saturday will be partly cloudy with sunny intervals and top temperatures reaching 20 degrees C, but the rain will return on Sunday with light showers in the morning, clearing in the afternoon