Heavy rain in Wellington caused surface flooding on roads in several parts of the city.
A slip blocked one track of the Johnsonville railway line on Monday morning. Buses were replacing trains until the slip was cleared.
Areas affected by surface flooding included the CBD and the suburbs of Kilbirnie, Karori, Hataitai and Miramar, Wellington City Council said.
Police also issued warnings of surface flooding to drivers in the lower North Island.
Fog blanketing parts of Christchurch delayed flights at Christchurch Airport.
A sharp wintry blast was making its way up the South Island on Monday bringing snow, very cold temperatures and strong winds.
MetService said there would be a brief return to wintery conditions in Fiordland, Southland, Otago and Canterbury with snow down to 500 metres in the far south and 600 - 700 metres in Canterbury.
MetService said the cold temperatures and snow would probably affect stock, particularly newborn lambs and calves. Motorists were advised to drive to the conditions on higher roads and passes.
The front was expected to quickly clear the South Island before reaching the lower North Island by Monday night.