Power outages in Whanganui's St John's Hill and Mangamahu

Trees in lines cause 25% of all power cuts - that's 70,000 customers without power each year because of trees on Powerco's electricity network. Photo / Bevan Conley

Residents in the St John's Hill and Mangamahu areas have no power on Tuesday morning.

Forty Powerco customers in St John's Hill are currently without power after a branch fell through an overhead line.

Power went out at 5.48am, with a field crew waiting until it was daylight to safely patrol the line to see where the damage had occurred.

Arborists are currently cutting branches from the tree that is close to the line, with power expected to be restored this morning.

Field crews are also working to restore power to 35 Mangamahu customers.

Power was cut to 125 customers at 5pm on Monday and was progressively restored to 67 customers by 8pm.

However, the weather conditions made it too unsafe to continue repairs overnight, with crews back on the scene this morning.

Power is expected to be back on to the remaining customers by noon today.

Trees in lines cause 25 per cent of all power cuts, affecting 70,000 customers in Powerco's network each year.

It was important for property owners to keep trees clear of overhead lines, Powerco senior vegetation manager Colin Winch said.

Much of Powerco's North Island network crossed some of the country's toughest rural terrain, which was at its most vulnerable during windy conditions, Winch said.

"If left uncut, and allowed to grow close to power lines, trees can be a serious hazard – not only causing power cuts for your community, but there's the risk of electrocution, serious injuries or fires."