Firefighters pumped water from homes in Dafen near Llanelli
Much of Wales has had the wettest August since 1992, and sunshine levels are among the lowest on record.
While an average Welsh August has about 106mm of rain, figures show that up to 26 August there had been almost 180mm.
Wales has been wetter than both England and Scotland, and outstripped by only Northern Ireland, which has had over double its average rainfall.
The blame is partly put on the jet stream bringing weather systems across the Atlantic being further south.
The unseasonal weather affected major events such as the National Eisteddfod in Cardiff on some days.
Heavy rain also saw homes being flooded in Aberystwyth and Llanelli, while a school was flooded near Aberaeron.
An annual harness racing festival in Ceredigion was cancelled because of bad weather for the first time.
One of the world's most eminent climatologists, Sir John Houghton, has said people must get used to intense rain and floods as global warming tightens its grip.
But not all of Wales has been a washout in August with some areas, particularly parts of north-east Wales, seeing close to average rainfall.
While August has been mostly grim, May was warmer and drier than normal and June was actually sunnier than average.
July, however, was much wetter than average, although levels of sunshine were only slightly below normal.
BBC Wales weather forecaster Derek Brockway said the reasons for the poor summer were complicated but the jet stream, strong air currents in the atmosphere, had probably played a big part.
Northern Ireland: 195.1mm
Up to 26 Aug (Source: Met Office)
"The jet stream steers weather systems across the Atlantic and normally it would go up between Iceland and Scotland bringing low pressure in that area," he said.
"We would normally get high pressure from the Azores but that has not really happened this year.
"This year the jet stream has been further south bringing low pressure and rain to Wales."
The wettest August on record was in 1917, when 274.3mm of rain fell.
England has been drier than Wales in August with 101.6mm, while Scotland has seen 152.5mm.
Only Northern Ireland has had a wetter August with 195.1mm, which is more than double what it would usually expect for the whole month.
It has been a difficult month for businesses which depend on good weather.
Clive Bailey, of Bailey Balloons which operates hot air balloon flights, has seen a huge number of flights cancelled this month.
"We've had to cancel flights because of ground conditions," he said
"We use Llanarth Village Hall [in Monmouthshire], there's a football pitch there we use as a launch site but the ground is too soft for Land Rovers.
"There's also the continual poor weather.
"We would have done 30 or 40 flights in August usually and we've done four, it's been that bad."
But some parts of Wales have fared better than others, with Flintshire seeing average rainfall for August.
Higher areas have tended to get a lot of rain, such as parts of Gwynedd and the south-east Wales valleys, and parts of Pembrokeshire and Carmarthenshire have also had a soaking.
Mr Brockway pointed out, however, that August is usually the wettest summer month in Wales anyway.