Further support has been promised from London as work continues to repair damage caused across Northern Ireland by Storm Eowyn.
On Sunday evening, more than 75,000 people remained without power and work continued to clear fallen trees from roads.
Stormont Education Minister Paul Givan said a small number of schools will be unable to open on Monday, but the majority should be able to reopen by Tuesday.
He said there have been 154 reports of damage of school buildings, and around 80 schools are without power.
Additional engineers have been brought to the region from Great Britain to help NIE Networks to restore power.
Some 52 engineers from England had been scheduled to arrive on Saturday, with 30 to be utilised by NIE and 22 to assist ESB Networks in the Irish Republic, and further resources to follow.
NIE Networks said it has more than 1,000 staff including 700 in the field working to restore supplies to customers as quickly as possible.
Northern Ireland Secretary Hilary Benn said further support is coming from Great Britain.
He said ministers from a number of UK Government departments, led by the Chancellor of the Duchy of Lancaster Pat McFadden, were working to assist NI Executive ministers.
Prime Minister Sir Keir Starmer spoke with First Minister Michelle O’Neill and deputy First Minister Emma Little-Pengelly on Saturday afternoon.
On Sunday, Mr Benn said more engineers were on their way to assist and further requests are being examined.
“The scale of the damage wrought by this storm is deeply concerning, and I want to express my sincere gratitude to all those working hard to restore electricity, clear fallen trees and debris and keep people safe,” he said.
“I am pleased that under mutual aid arrangements, specialist engineers from England are already in Northern Ireland to assist with the urgent effort to restore power to communities and more are on their way.
“We are also examining how we can assist with other requests made by the Executive and Northern Ireland Electricity for equipment and personnel.”
He added: “I will continue to work closely with Cabinet colleagues and Northern Ireland Executive ministers in the days ahead to make sure we are doing all that we can to support those affected.”
The storm has damaged more than 100 schools and over 2,300 obstructions on the road network were reported, with 70 trees having to be cleared on Friday just to reopen the M2.
Ms O’Neill and Ms Little-Pengelly visited NIE Networks in Craigavon on Saturday afternoon to thank workers.
The First Minister described the storm and its impact as “unprecedented on every level”.
“People will continue to work tirelessly to ensure people are reconnected as quickly as possible. It is very difficult given the sheer volume of damage that has been caused but we’re assured that all the work that can be done is being done and we want to thank the staff for all of their efforts,” she said.
Ms Little-Pengelly welcomed the additional engineers, and said officials will be emphasising the need for support for Northern Ireland in meetings with the Prime Minister and political leaders across the UK.
The reconnection task was expected to be challenging on Sunday after the Met Office issued a yellow warning for strong winds across Northern Ireland, with potential disruption to transport and infrastructure.
That weather warning applied from 10am to 7pm, while a yellow warning was issued for snow and ice from 6pm on Saturday to 10am on Sunday.
Red weather warnings were issued on Friday and significant damage hit infrastructure and homes across Northern Ireland.
At the peak of the damage, 30% had lost power.
On Sunday afternoon, NIE Networks said approximately 75,000 customers remained without electricity.
They said power had been restored to 210,000 properties.
Please remember our safety message and do not approach any damaged electricity equipment
Derek Hynes, managing director of NIE Networks, said managers believe it will take 10 days to complete the task.
“We are still visiting locations where damage has been caused and are working on the faults that will get power back to the highest possible numbers of homes and businesses,” he said.
“Assessments carried out on the network yesterday have now enabled us to put restoration details on our website. Please check Power Check on our website (nienetworks.co.uk) for an initial estimate of when we will get power back for your location. We will work to refine these dates and times further as we go through the next few days.
“From what we are seeing so far, we believe that it will be around 10 days by the time we complete the repairs needed to get power back to everyone.
“Please bear with us as we work through the yellow weather warning over the course of today. We will continue to work with the strategic and tactical co-ordination groups so that we can avail of as much help as possible from other agencies.
“Councils across Northern Ireland have also opened community assistance centres in their areas at which NIE Networks will be in attendance. These details can be found at www.nienetworks.co.uk.”
Mr Hynes urged the public not to approach any damaged electricity equipment and to be careful around fallen trees.
“Please remember our safety message and do not approach any damaged electricity equipment,” he said.
“Please be extra careful around fallen trees as they often take electricity poles and wires with them as they fall, and call us if you see anything that looks dangerous on 03457 643 643.”
