Dangerous weather conditions are hampering efforts by lines' crews to get power back on for some of the nearly 4000 Northland houses affected by Thursday night's storm.

Whangārei and Kaipara lines' company Northpower is appealing to customers to keep their trees well clear of powerlines to avoid unnecessary outages and inconvenience to others.

That's because trees were again the major cause of electricity outages on Thursday night in Kaipara and Whangārei where 1790 households were without power for various lengths of time when howling winds and rain wreaked havoc in the region.

More bad weather was forecast for last night.

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The west coast in particular was badly affected on Thursday and Top Energy said further outages were likely with more rain forecast over the weekend.

A shed blew into a power pole and knocked it over in South Hokianga while trees downed powerlines in South Hokianga.

"Conditions remain challenging – particularly with access into Mitimiti where flooding is impeding progress, and where poles need to be replaced," Top Energy spokeswoman Philippa White.

She said gale force winds have largely impacted parts of the network in the Hokianga, particularly Mitimiti and Omanaia, but also pockets in Kaikohe and Pakaraka.

Outages were caused by trees getting into the lines, broken cross arms, damaged and in some instances, lines were brought down, she said.

"We urge people to ensure they keep their trees and vegetation well clear of our powerlines by trimming or felling them. Spring and summer months are ideal for having this work completed," Northpower spokesman Steve Macmillan said.

MetService meteorologist Rob Kerr said the winds would start dying down from this afternoon and turn to northwesterlies from tomorrow which should be a warm and wet day.

He said Northlanders would still experience gusts this morning but they wouldn't be as strong as last night.

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