Around 2,000 customers are without power following lightning strikes.
ESB Networks say the majority are in Roscommon, which will be restored by later tonight.
Around 400 customers in north County Dublin will be without power overnight and crews will work on the repairs from first light.
Flooding has also been reported in Leitrim, Donegal, Cavan and Longford.
A number of roads in Carrick-on-Shannon are said to be flooded and AA Roadwatch have said that conditions are particularly treacherous on the N4 Sligo/Dublin Road approaching the town from the Boyle side.
Spot flooding has hit the N13 Ballybofey/Letterkenny Rd at Kilcross in Co. Donegal as well as local roads in Cavan town around Lough Gowna.