The two victims of Saturday’s storm were killed in separate incidents when trees fell on their vehicles in Lancashire and the West Midlands.
The Energy Networks Association said on Saturday evening that 259,000 customers were still without power.
It added that engineers would be working through the night said they would be working through the night and into Sunday to restore power.
Northern Ireland Electricity Networks said more than 20,000 properties were without power on Saturday evening and warned it may take days for supplies to be fully restored. At the storm’s peak, more than 48,000 premises were affected.
Sixty-four flood warnings – meaning flooding is expected – and 147 flood alerts are in place for parts of England following heavy rain, according to the Environment Agency, external.
In Wales, which is still recovering from the flooding left by Storm Bert last month, Natural Resources Wales says 25 flood warnings and 49 alerts are in force, external. The Scottish Environment Protection Agency has two flood warnings in place, external.
Disruption to train travel is also expected to continue, with National Rail warning passengers to check their journeys before travelling.
It said there is likely to be “significant disruption with heavy rain and wind” to services in south-west Scotland, north and south-west England and Wales.
Operators including Chiltern Railways, Great Western Railways, Northern, LNER and Transport for Wales currently face delays and cancellations.
Belfast International Airport said that a full flight schedule is planned for Sunday but it could be subject to delays.
Storm Darragh was the fourth named storm of the season following Bert and Conall last month.