KEY POINTS:
The heaviest rain of the summer could fall today as rain lashes the country from the Westland ranges to the Waikato with up to 180mm falling in some areas.
MetService is warning that heavy rain will fall in the Coromandel, North Island high country, Bay of Plenty, and the Wairarapa as well as parts of Canterbury and Marlborough.
Police in Wellington and the central North Island are warning motorists to drive to the conditions.
Sergeant Andy Dow said drivers should watch their following distances and watch out for surface flooding.
Shortly before midday, police warned of surface flooding at the Tawa off ramp on State Highway One, north of Wellington.
MetService forecaster Gerard Barrow said a trough and deepening low would move southeast over central New Zealand today, bringing moist subtropical air.
He said rain falls were expected to be between 90 and 180mm with the heaviest falls on the upper slopes of Mt Taranaki and Ruapehu.
Mr Barrow said the heavy rain could last until Friday in the Bay of Plenty.
He said the South Island, from Canterbury north, is also in for a drenching and up to 120mm could fall around the headwaters of Canterbury.
"For many areas this is likely to be the heaviest rain for the summer and people should be prepared for streams and rivers to rise quickly," Mr Barrow said.
Wanganui and Palmerston North are preparing for a second dose of heavy rain following substantial flooding in both areas on Tuesday.
Wanganui Mayor Michael Laws yesterday said council infrastructure staff were making preparations in case of flooding, including organising a supply of sandbags, clearing sumps and checking key structures.
The council also advised the public to clear gutters on their homes, drive carefully and slowly through areas of surface flooding and keep children away from flood-affected areas.
Several Palmerston North streets flooded on Tuesday as heavy rain overloaded the city's stormwater system.
The MetService said 56mm of rain fell in Wanganui in six hours on Tuesday and 49mm in Palmerston North in a five-hour period.
- NZHERALD STAFF and NZPA
