The wettest summer - defined as June, July and August - since national records began was in 1912.
Figures up until 29 August show that 366.8 mm of rain fell across the UK this summer, compared with 384.4 mm rainfall in 1912.
The April to June period was also the wettest recorded in the UK.
The figures are provisional as there are still two days remaining in August, but the BBC Weather Centre said the rainfall was not expected to exceed the total amount in 1912. Records began in 1910.
BBC weather presenter Laura Tobin said this summer had been so wet because a jet stream - a fast moving band of air high in atmosphere - from America, which should be sitting across Scotland and the north of England, was much further south this year.
"It meant June was the wettest on record - most places had over one-and-a-half times more rain than they should have.
"July was also one of the wettest months ever, with some areas like Dorset breaking records. August has been about average," she said.
She said September was expected to be a typical September, and no heatwave was expected in the next 10 days.
In April, seven water companies across southern and eastern England brought in hosepipe bans after two unusually dry winters left some groundwater supplies and rivers as low as in the drought year of 1976.
But the restrictions were followed by record rainfall across the UK in April, and more rain in May and June led to flooding in some areas. The hosepipe bans were lifted in June and July.
The Environment Agency issued more than 1,000 river flood alerts and warnings between 1 June and 15 July, the most issued in a summer since 2007.
August 2012 looks set to be the driest and sunniest of the three summer months across the UK, with 105.5 mm of rain to 29 August, and 140 hours of sunshine up to 28 August.
The mean temperature for August was 15.7 Â°C - in a month that also saw the hottest day of the year so far, reaching 32.4 Â°C at Cavendish, Suffolk, on 18 August.
Summer 2012 is also likely to be one of the dullest summers on record, with just 399 hours of sunshine up to 28 August.
It is the  dullest summer since 1980, when the UK saw only 396 hours of sunshine.
This summer is set to be the second wettest in the UK since records began - and the wettest summer in 100 years - provisional Met Office figures suggest.