A power outage caused by lightning strike plunged thousands of households and businesses in Maungaturoto into darkness.
Two Transpower-owned transmission circuits were struck by a lightning about 9.40am yesterday but electricity was back on after about 40 minutes.
Transpower spokeswoman Rebecca Wilson said although repairs were carried out promptly, it took some time for the company to restore power to all those affected.
About 80 lightning strikes an hour were recorded by Transpower engineers and Ms Wilson said the number indicated the severity of weather conditions in Northland from over the weekend.
Students at Maungaturoto Primary School were affected shortly after starting their day. Principal Shane Campbell said: "We were in the middle of doing the school newsletter so we couldn't continue to work on them. Some classrooms were doing computer work which they couldn't continue as well."
More than 100 lightning strikes accompanied rainfall of up to 100mm in some areas in Northland on Wednesday.
The front moved southwards over the far southeast of Northland, Auckland and Coromandel yesterday, bringing heavy thundery rain south of Whangarei.
A Waipu Cove resident's rain gauge measured 70mm of rain in one hour yesterday morning.
Rain is expected in Whangarei, Kerikeri, Kaitaia and Dargaville for the rest of this week, with highs of 18C and lows of 10C.