"Storm Arwen" -- which hit the region late Friday, killing three people -- initially knocked out power for hundreds of thousands of homes following wind gusts of almost 100 miles (160 kilometres) per hour.

By Wednesday morning, engineers had reconnected 97 percent of the properties, but around 30,000 were still without power, the Energy Networks Association (ENA) said.

Some may not have their power back until the end of the week, it added.

"We have incredibly dedicated teams of engineers who have been working all round the clock to restore the network,"

"The scale of the restoration effort engineers are facing is enormous," Business Secretary Kwasi Kwarteng told MPs, adding that the wind speeds recorded in central Scotland "have only been seen twice in the last 25 years".

He called Arwen "an event the like of which we haven't seen for 60 years".

"We have to be prepared for similarly extreme difficult weather conditions in the future. We have to make sure that our system is resilient," Kwarteng added.

Police said falling trees killed three men when the storm hit late Friday -- one in northwest England, one in Scotland and the third in Northern Ireland.