Transpower expects work to restore a key transmission line into Northland will resume Sunday morning after experiencing delays.

A pylon fell near Glorit on Thursday, causing region-wide outages affecting thousands of residents.

Transpower says it made good progress to raise a temporary tower on Friday, but was not able to transfer all of the conductor wire to it before the weather turned and it became dark.

"It is complex and challenging work and we have encountered delays that mean we weren't able to complete the work before it got dark and the weather deteriorated," general manager of grid delivery Mark Ryall said on Saturday.

"To ensure the crews can complete the work safely, the final works will be delayed until tomorrow morning."

Lines companies Northpower, Vector and Top Energy have all encouraged customers to continue saving power.

Transpower said crews were on track to meet Sunday's deadline and there was sufficient supply to meet the weekend demand. Further repairs on Sunday would ensure there was enough capacity to handle Monday morning's expected rise in demand.

"We thank Northland communities for their continued patience. I know it makes a big difference to our crews putting in the hard work on the ground," Ryall said.

MetService said the forecast for the region was for early morning rain, easing to the odd shower and clearing up in the afternoon.

The cause of the tower's collapse remained unknown.

This story was originally published by RNZ