Heavy rain is predicted to continue lashing parts of the South Island, with thunderstorms and tornadoes possible around the country.
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The MetService has issued a severe weather warning for Westland from Otira southwards, with up to 100mm of rain expected to fall in the area by Thursday night.
It says rain could reach peaks of 25mm per hour, especially in thunderstorms.
A heavy rain watch has also been issued for the Tararua Ranges, Westland north of Otira and Buller, and Canterbury Headwaters south of Arthurs Pass for Thursday.
The forecaster is also watching for thunderstorms from Waikato to Wellington, with a chance they could become severe on Thursday morning.
About 4000 people were left without power in Wellington's northern suburbs after a lightning strike on Thursday morning, although that number had been reduced to about 1000 by 7am.
Further south, Buller, Westland and Fiordland may also be in for thunder and downpours of up to 35mm/h. At peaks it may also cause flooding, the MetService said.
"Localised tornadoes may cause damage to buildings, trees and power lines."
It comes after a number of homes were hit by lightning in the North Island earlier in the week and a small tornado tore through the West Coast township of Arahura.