It has been a wet spring, with Dunedin having its soggiest November on record.
NIWA's Chris Branolino tells TVNZ's Breakfast they've had to look way back in the history books to work out just how wet it's been.
“These records don’t just go back 10, 20 years they go back to the early 1900s and late 1800s.
The weather expert says easterly winds are one of the major causes of the rain.
The forecast means some of those affected will have to delay the clean-up.
"The east of the South Island has received two to maybe three or four times their normal rainfall."
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Places in the North Island and South Island should expect to get a dumping of rain today.
“We are going to see more of those hit or miss thunderstorms and downpours today in upper North Island.
“The South Island will also get a lot of rainfall and the lower eastern part of the North Island, Wairarapa and Tararua ranges."
He said it was took early to make Christmas Day prediction.
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