The Met Office has defended its forecasting after conceding that weather advice given to the Government was "not helpful".
The admission, revealed in a Freedom of Information request, came after April 2012 became the wettest on record despite a forecast sent to contingency planners suggesting it was likely to be drier than usual.
The three-monthly outlook issued by the Met Office had stated: "The forecast for average UK rainfall slightly favours drier than average conditions for April-May-June, and slightly favours April being the driest of the three months."
However, in a memo after the event, the Met Office said: "Given that April was the wettest since detailed records began in 1910 and the April-May-June quarter was also the wettest, this advice was not helpful."
The prediction was made as part of a three-month forecast that is no longer made public after the Met Office was lampooned for its "barbecue summer" claim ahead of the less-than-balmy summer of 2009.
Julia Slingo, chief scientist at the Exeter-based Met Office, said the long-range forecasts were "probabilistic" and "experimental" and were helpful on around 65% of occasions.
"You have to, of course, with probabilistic forecasts, look over a large number of events and we do that and on about 65% of occasions we do give indeed very helpful advice," Ms Slingo told BBC Radio 4's Today programme.
"I think it was quite right that we looked at this particular forecast last year because in March we were facing really very serious pressures on water resources – a major drought that had been going on for nearly a couple of years – and I felt when I looked at the seasonal forecast at that time that I would be not being fair to the Government if I didn't emphasise the fact that we did see a slightly enhanced risk of the drought continuing.
"Likewise, I did also emphasise that there was also quite a chance that April would also be wetter than normal but in the context of where we were at that particular point as a country I felt it was right to emphasise the risk of dry conditions continuing as a precautionary principle."
In a lengthy explanation on the Met Office website, it said the long-range "outlooks" were "never used in isolation" but alongside regular monthly outlooks and "highly accurate" short-term forecasts and warnings.
It said: "The science of long-range forecasting is at the cutting edge of meteorology and the Met Office is leading the way in this research area.
"We are continuing to work hard to develop the science of long-range forecasting. We are confident that long-range outlooks will improve progressively and that the successes we have achieved in other parts of the world already will, in the future, be mirrored in the UK.
"The Met Office constantly reviews the accuracy of our forecasts across all time scales and is recognised by the World Meteorological Organisation as one of the top two national weather forecasting services in the world."
More accurately, and based on readings up until Tuesday, the Met Office forecast that March would be the second coldest in the Westcountry since records began in 1910.
While mean temperatures in Devon and Cornwall have been significantly above the UK average of 2.5C (36.5F), the month will be second only to 1962 as the coldest.
Cornwall's mean temperature has been 5.1C (41.2F) some 2.3 degrees lower than the 30-year average. The mean temperature in Devon was down 2.7 degrees to 4C (39.2F) this month. In 1962 the figures were 3.9C (39F) and 3.1C (37.6F) respectively.
The Met Office said this March was likely to be the fourth coldest on record for England, joint third coldest for Wales and joint eighth coldest for Scotland.
The cold weather is expected to continue through the Easter weekend and into April, a spokesman said.
