The week ahead could be a washout for many, with half a month's rain expected to fall in a single day in some parts of the country.
Forecasters say Tuesday will be the wettest day of the week in southern areas, with up to 25mm (one inch) of rain possible in Devon, Cornwall and Wales.
Sky meteorologist Chris England said: "That's quite a lot of rain and could lead to some local flooding, but it's coming after a fairly dry spell, so any impacts are likely to be very limited."
Heavy downpours are possible in the East and the South East, although Scotland will be drier after heavy showers on Monday.
Temperatures will struggle to reach double figures anywhere on Tuesday, although conditions will improve towards the end of the week, when many places will have a mixture of sunshine and showers.
The first three months of the year have been exceptionally wet for many parts of the South West.
According to provisional Met Office data, 282.9mm of rain fell in Camborne, Cornwall, between January and March - the most since 2007.
In Chivenor, Devon, the figure was 211.8mm - more than 50% higher than the same three months in 2012.
However, forecasters warned against early predictions of a summer as damp as last year.
Dr England said: "Long range forecasts are a work in progress at the moment - they're better than tossing a coin but not by much.
"They're of benefit to utility companies over the longer term, for example, but they're not really meaningful to the person in the street.
"At the moment, it looks like there'll be a warmer, drier spell later in the month, especially in the south, but that can't be relied upon."