The MetService says heavy rain about the Tararua Ranges is expected to ease early on Saturday evening.
However, the forecaster says another 30-50mm - on top of the 100mm that has already fallen - is possible before 7pm on Saturday.
It says people in the area are advised to watch out for rapidly rising rivers and streams.
Meanwhile, rain about the ranges of Buller and Nelson and in Wellington has eased.
Similarly, the northwest gales in the Wairarapa region have eased and a wind warning has been lifted.