A DELUGE of early morning rain has left part of the country under water. Intense rain swamped homes and roads in many parts of Cork city and county while boats were used to rescue families from flooded homes in Belfast overnight.
Dublin and eastern parts of the country escaped the worst of the downpours but Met Eireann say that they can expect heavy rain tonight.
Thundery falls could cause problems for commuters in the capital by this evening.
Hundreds of Cork homes were left flooded or cut-off by flood waters today as torrential overnight rainfall caused chaos.
Met Eireann forecaster Evelyn Cusask said local heavy thundery rain are likely to continue as the weather stays very unsettled.
"It's being caused by warm air from Spain clashing with Atlantic air which is trying to get in," she said.
"In Cork they had 50mm of rain in two hours. The ground was already sodden after three times the normal amount of rain for the month. It's been the wettest June on record," she said.
In Northern Ireland, golf fans were drenched today as the golf course in Portrush hosting the Irish Open has received a pounding from intense rains.
Surface water on roads in several parts of Ireland caused problems for motorists this morning. In the Naas area, gardai said a number of cars spun off local motorways.
"People have been driving too fast and they've been spinning off the road. Thankfully were have been no injuries. Motorists should slow down and turn on lights in heavy rain," said a local garda.
It will remain cloudy tonight with scattered heavy showers and a risk of further heavy, thundery falls especially in the east, with fog patches.
Tomorrow the rain will be mostly scattered and light with heavy showers at night, especially in the west.
Saturday will be cooler with passing heavy showers. But at least Sunday looks like being a nice day, being mostly dry with sunny spells. And "a big improvement" is promised for next week.
Cork city suffered the equivalent of almost three weeks rainfall in a matter of hours with drains, culverts, streams and rivers totally unable to cope with the downpour.
The city and county now faces a clean-up bill that could run to over €1m -- with further heavy rainfall predicted over the next week.
Thousands of homes had their electricity supply cut off as a safety measure as flooding worsened.
Such was the scale of the flooding that an ESB sub-station in Douglas had to be shut-down -- with several pubs in Douglas village including Barry's and O'Driscolls left under almost two feet of flood waters.
Lightning struck the roof of St Stephen's Hospital in Cork, causing a fire. The blaze was brought under control but two people had to be treated for smoke inhalation.
Floods also hit parts of north and west Cork -- and left some rural roads totally impassable.
Clonakilty was left totally cut-off by flood waters -- with the emergency services co-ordinating essential access for the sick and elderly.
Roads near Mallow were described as treacherous due to flooding though the town's new flood defence system prevented major damage.
However, Cork Co Council is now carefully monitoring the levels of the Rivers Lee, Blackwater and Bandon amid fears of further flooding.
Gardai urged motorists to slow down -- and only undertake essential journeys given the flooding on main and secondary roads.
Greenmount resident Mary Murphy said locals couldn't believe their eyes this morning.
"I looked out the window and there was a river where the road had been," she told the Herald.
Children eager to view the flooding were urged to stay away from drains and culverts with several resembling raging torrents.
Dozens of roads were left impassable and gardai urged motorists to expect major delays throughout the day.
Near the Viaduct, an ambulance ferrying a patient to Cork University Hospital (CUH) required 4X4 assistance to get through heavy flooding.
In the North, where Irish Open tickets had been sold out for the showdown at Royal Portrush, intense rains caused problems.
Most main routes in south and east Belfast were left impassable after the heavy rain.
Cars were submerged during a massive downpour yesterday evening. Around 1,000 homes lost electricity temporarily and residents battled frantically using boards, brushes and whatever came to hand to try to keep back the rising waters.
Even a police vehicle in West Belfast was submerged and officers had to be rescued from the rooftop.