Civil Defence agencies in the South Island are on standby, with significant rain and wind expected in several areas from this afternoon.
Thunderstorms have already begun in the upper North and upper South Island today as a series of active fronts and troughs pass over the country.
MetService has reported 1233 lightning strikes in 120 minutes.
A red alert has been issued for Canterbury with up to 300 millimetres of rain expected in the high country and up to 120 millilitres about the coast and plains. The heavy rain is forecast to start tonight and continue until late Monday.
Niwa is forecasting a rapid increase in river flows across the region tomorrow.
North Canterbury and the Kaikōura coast were expected to be the worst affected.
MetService has also warned that a combination of king tides and strong northwesterlies may bring coastal inundation to Auckland this weekend.
Nelson's emergency personnel say rain has been falling this morning, but it has not been a problem so far.
West of Motueka, heavy rain is forecast to continue until 8pm tonight., while for the Richmond Ranges, rain should continue until 11pm.
On the West Coast, Civil Defence is meeting now and is expected to provide an update soon.
The Transport Agency says it is prepared for possible flooding and is urging South Islanders in particular to take care on the roads.
RNZ
