The new figures for the calendar have revealed that 171.6cm of rain fell in Wales, despite a bone dry start to the year.
2012 was the wettest year on record for England but only 17th wettest for Scotland and 40th wettest for Northern Ireland.
It meant that overall, last year was the second wettest year in the UK since 1910, and just a few millimetres short of the record set in 2000.
The frequency of extreme rainfall in the UK may be increasing, according to analysis by the Met Office.
Four of the top five wettest years have occurred since 2000.
Statistics show that days of particularly heavy rainfall have become more common since 1960.
The analysis is still preliminary, but the apparent trend mirrors increases in extreme rain seen in other parts of the world.
Extreme rain is defined as the sort of downpour you would expect once in 100 days.
There are big swings in rainfall from year to year, but the overall trend is upwards since 1960. Last year, for instance, extreme rain fell around once every 70 days.
Scientists say that as the world has warmed by 0.7C, the atmosphere is able to hold 4 per cent more moisture, which means more potential rain.
The change in the UK trend is slight, but if the trend is confirmed it will clearly increase the risk of flooding.
Wales was hit by severe flooding in June, in the Aberystwyth area, and more recently in North Wales. Land use and development also impacts on flooding and its severity.
Professor Julia Slingo, chief scientist at the Met Office, said the preliminary analysis needed further research but was potentially significant.
"We have always seen a great deal of variability in UK extreme rainfall because our weather patterns are constantly changing, but this analysis suggests we are seeing a shift in our rainfall behaviour," she said.
"There's evidence to say we are getting slightly more rain in total, but more importantly it may be falling in more intense bursts - which can increase the risk of flooding."
Although it felt like a year of deluges in Wales, what actually fell was only 18 per cent more than the long-term average.