Forecasters have warned that heavy rain and severe storms will happen more often as a result of climate change.
Last year was the second wettest on record in the UK as a whole, with total rainfall of 1,330.7mm (52.4ins).
In Scotland an unusually dry summer in the north-west meant 2012 ranked only 17th on the all-time list, but 2011 was the wettest in recorded history.
The Met Office said average long-term rainfall in the UK increased by about 5% between the periods 1961-1990 and 1981-2010. Four of the UK's five wettest years since records began in 1910 have been since 2000.
The occurrence of "extreme" days of rain, in which large amounts fall in intense downpours, also appears to have become more frequent.
The trend, which has seen four of the UK's five wettest years on record happen in the 20th century, would lead to more flooding and make conditions more challenging for farmers and wildlife.
The Met Office said rising global temperatures could be playing a part in increasing rainfall, as a warmer atmosphere can hold more moisture and increase the potential for heavy rain.
The world has seen temperatures rise by around 0.7C since the beginning of the Industrial Revolution, which would equate to around a 4% increase in moisture in the atmosphere.
STV forecaster Sean Batty said a number of factors were responsible for the increase in episodes of extreme rain.
He said: "It's possibly down to less sea ice being around, a warmer ocean, a slightly warmer atmosphere as well.
"Obviously a warmer atmosphere can store more water and that's potentially why we're seeing more extreme rainfall events now."
Professor Nigel Arnell, Walker Institute director at the University of Reading, said last year's weather fitted a pattern which has seen rainfall increase in recent decades in many parts of the northern hemisphere.
"While rainfall varies naturally from year to year and decade to decade, there is increasing evidence that the build up of greenhouse gases in the atmosphere is starting to affect rainfall across the globe," he said.
"That means we are likely to see flood frequency increase further."
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