Almost 2,000 people are without power and some flights have been cancelled or diverted as Storm Desmond hits Ireland.
A gust of 118km/h was recorded at Mace Head off Galway as the storm continues to batter the west coast.
There are reports tonight of spot floods and surface water on roads in Barna, Spiddal, Salthill, Loughrea, Tuam and Portumna.
The power outages are mainly along the west coast where a Status Red rainfall warning is in effect.
The worst hit areas are the Kinsale/Bandon region in Cork with 1,200 people without electricity.
Nearly 3,000 customers in Baltrasna, North Dublin were without electricity but power has now been restored.
ESB Networks has apologised for any inconvenience caused by the power outages, and advised the public to be cautious and not approach any broken lines or damaged polls.
It said that power outages can be reported to the ESB via its emergency contact number on 1850 372 999.
Cork Airport has said high winds forced the cancellation of inbound Aer Lingus regional flights from Birmingham and Glasgow as well as outbound to Glasgow.
Waiting on the tarmac at Manchester Airport after two failed landing attempts at Dublin. #stormdesmond— Sandra Hurley (@sandra_hurley) December 4, 2015
A month's rainfall is expected in parts of the northwest over a 36-hour period as Storm Desmond hits and Met Éireann issues a status Red rainfall warning.
Met Éireann has issued a Status Red rainfall warning for areas of Connacht as well as counties Donegal, Clare, and Kerry as the fourth storm of the winter approaches.
The alert predicts in excess of 70mm of rain, likely to give rise to severe flooding in some areas.
The head of Met Éireann's general forecasting has said parts of the northwest will get a month's rainfall over a 36-hour period with the arrival of Storm Desmond this evening.
Speaking on RTÉ's News at One, Gerald Fleming said it is the first time the forecaster has issued a status red warning for rainfall since the coding of weather warnings began.
V windy & blustery overnight with widespread rain, heavy in western coastal counties. Some flooding expected with dangerous driving....— Met Éireann (@MetEireann) December 4, 2015
... conditions. SW winds will be strong to gale force & v gusty, with the most severe winds in W & NW coastal counties. Lows 9 to 11.— Met Éireann (@MetEireann) December 4, 2015
Mr Fleming said parts of the west and north are expected to be hit the hardest, with between 70 and 100mm of rain forecast. He said spot flooding will be inevitable in those areas.
The normal monthly rainfall for December is between 60 and 120mm, depending on the part of the country.
Strong winds with speeds of 55 to 75km/h and gusting to 100 to 120km/h are also forecast throughout the period.
Status Red warnings are relatively rare and are issued to alert people to take action to protect themselves and/or their properties. The warning will be in effect until the early hours of Sunday morning.
— RTÉ News (@rtenews) December 4, 2015
The Road Safety Authority has advised drivers to check local and national forecasts and traffic updates before setting out.
It has warned drivers to be aware of possible fallen trees and to avoid driving through flooded areas.
Multiple weather warnings issued, including Status Red rain warning for some western areas.
Status Red Rainfall Warning for Connacht, Donegal, Clare & Kerry from 6pm until 3am Sunday. This is the most severe weather warning possible— AA Roadwatch (@aaroadwatch) December 4, 2015
Where roads become flooded, conditions may be extremely hazardous and motorists are advised to approach flooded roads with extreme caution.— An Garda Síochána (@GardaTraffic) December 4, 2015
Gardai are advising that only essential journeys should be made tonight.
Kerry's Severe Weather Assessment team met twice today to assess and prepare for any potential fallout from Storm Desmond. They are also coordinating both regionally and locally with all the other statutory agencies, including the HSE and the gardaí.
Since late afternoon there have a few reports of minor weather related incidents including some trees down - on the Duagh and Dromin roads - but they have since been cleared.
In County Cork, where there is a Status Yellow warning in place, flood defence staff in Mallow and Fermoy are on alert but it is felt the west of the county is more vulnerable with council staff in six West Cork towns on standby. These include Bantry, Schull, Skibbereen, Clonakilty, Castletownbere and Dunmanway.
The county's Severe Weather Assessment team met this morning to assess the situation and are scheduled to speak again at 10am tomorrow morning.
In Cork City, gardaí report that while the city routes were busy these evening, there was no repeat of last night's chaos in which several thousand motorists endures delays of up to three hours because of flooding on the M40 leading to the Jack Lynch Tunnel.