There is extensive flooding in parts of Co Mayo following several hours of torrential rain.
Gardai in Castlebar say a number of roads are flooded and there has been at least one road accident near Newport.
The worst hit areas are the Castlebar-Westport Road, the Castlebar-Glenisland Road and the Castlebar-Newport Road.
A spokesman at garda divisional headquarters in Castlebar appealed to motorists to avoid travelling on these roads until conditions improve.
Gardaí in Westport say they believe a number of people sustained minor injuries in the road traffic accident near Newport.
Four units of Mayo fire brigade dealt with flooding in the Castlebar Newport area.
At Glenisland one of the units rescued a man who had been trapped in his house.
It was surrounded by about one metre of water.
Another unit attended the scene of the road traffic accident near Newport. Three people who were travelling in a 35-seater coach sustained what are described as minor injuries.
Earlier in Co Galway two people had a lucky escape when their house on Gorumna Island was struck by lighting, the mother and son were uninjured but the house was extensively damaged.
Water levels subside in Dublin
Meanwhile, a clean-up operation is under way in parts of Dublin following heavy overnight flooding.
View your photos of flooding in Dublin
Met Éireann says the worst of the rain is over and although more heavy rain is forecast tonight, a repeat of last night's rainfall is 'inconceivable'.
Some 15 days of average rainfall was recorded at Dublin Airport in one hour.
A number of homes in north Dublin were evacuated in the early hours of the morning due to the rising floodwaters.
However, water levels on roads, which caused major traffic disruption earlier, have now subsided in many parts of the city.
DART services have also returned to normal after flooding had caused disruption between Dalkey and Dún Laoghaire stations.
The Mater Misericordiae Hospital was also affected by the heavy rains.
The A&E department had to be closed following flooding and a roof collapsed in the old part of the hospital, forcing patients to be moved from one ward.
The hospital has asked the public not to attend its A&E until further notice.
It said people with outpatient appointments today should attend as normal, while those who are scheduled to have elective surgery should contact the hospital before leaving their home to check if their appointment has been affected.
Around 20 residents of Clanmoyle Road in Donneycarney were forced to leave their homes overnight.
The basements of the houses filled with flood water, which then overflowed. Walls in the gardens also collapsed.
Residents say they were still recovering from last year when their homes flooded following heavy rainfall.
Another 20 residents had to leave their apartments on Sherrard Street.
The Fire Brigade also attended a house in Monkstown, Co Dublin, where the roof had collapsed.
Early morning motorists described the worst-hit areas in Dublin as akin to 'swimming pools'.
Dublin City Council said potentially any house in the capital could have flooded overnight due to the torrential nature of the rainfall.
The spokesman said: 'Flood waters are alleviating at the moment and the high tide is below critical level so it should not cause a huge problem.'
Earlier, Dublin Fire Brigade has again warned motorists not to drive into areas where roads are flooded as there is a real risk they will become stranded.
Emergency staff were on standby since a weather warning was issued by Met Éireann at 2am.
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