"We would encourage people to be prepared for possible outages by having torches and battery powered radios at hand, mobile phones charged, fresh water available and gas cooking facilities ready.''
People can call in faults to Northpower on 0800 104 040. People should stay clear of downed lines and keep others away also.
Recorded outage and restoration updates will be listed on www.northpower.com/network/current-outages.
The National Institute of Water and Atmospheric Research (Niwa) said heavy rain was expected last night and into the weekend.
Northeast winds would drive significant rain to parts of Northland, Niwa meteorologist Ben Noll said.
Humidity of between 80 per cent and 90 per cent currently experienced in most parts of Northland, especially Whangarei, would continue until early next week due to the moist and humid air being blown from the Pacific, he said.
Rain in Northland is expected to clear on Tuesday next week.
Rainfall figures provided by the Northland Regional Council showed 91mm of rain Kaeo received in the 24 hours to 3pm yesterday was the highest in the region.
Waimamaku at Weka Weka Rd received 80mm, Ngunguru at Dugmores Rock and Waima at Tutamoe 59.5mm, and Waitangi at Wiroa Rd 58.5mm.
Areas that received the least rainfall were Oruru at the bowling club 10mm, Paparoa at Maungaturoto 12.5mm, Whakapara at Puhipuhi 16mm, and Veronica Channel at Opua Wharf 17mm.
"Rain in Northland will continue until Friday and then there'll be intermittent bursts through to Sunday. A low pressure system in the Tasman Sea is moving to New Zealand over the weekend and that will potentially bring thunderstorms to Northland," Mr Noll said.
"In terms of rain, it's going to be more hit and miss. There'll be some sunshine as well and people enjoying themselves outdoors may be interrupted by rain so the weather's going to be deceiving."
Northland Rural Support Trust co-ordinator Julie Jonker said it was hard to say whether the rain this week would be a drought-breaker because no one knew how much would fall.
But the outlook looked good for farmers who have moved from response to recovery phase, she said.
"They really need this rain without which soil moisture level will be in deficit. Pastures will recover, rivers will be back recording mean annual rainfall and the soil moisture deficit will improve," she said.
Mr Noll said farmers would be quite happy with the decent rain overnight Tuesday but warned some areas may have to brace for localised flooding.
"With the storm we have some areas will have too much rain but pinpointing those areas is a challenge in meteorological circles.
"Gusty winds in excess of 70km an hour are also possible in offshore areas of Northland, especially Whangarei and the southern areas of the Far North, over the weekend," Mr Noll said.