The newly-reopened quake-repaired State Highway One north and south of Kaikoura has been shut down for the day after rockfalls and surface flooding.
The highway, which was closed for more than a year after the magnitude 7.8 quake of November 2016, is closed to the south between Peketa and Goose Bay and between Clarence and Mangamaunu.
The NZTA said at 12.30pm today that it had decided to keep it closed for the rest of today.
The next update will be made at 7am tomorrow.
The inland road, Route 70 via Waiau and Mt Lyford, remains open as the road into Kaikoura.
Drivers travelling between Picton and Christchurch are encouraged to use the Lewis Pass alternate route, via State Highways 63, 6, 65 and 7, today and possibly tomorrow also, says NZTA journey manager Tresca Forrester.
"We have more certainty around this route in the current weather," she said.
Another band of rain is forecast for early afternoon into tonight which may affect the highways closures so drivers should continue to check routes before heading off.
Around 76mm of rain fell on coastal Kaikoura since midnight yesterday. The forecast is for rain to ease off followed by a second wave later today and tonight.
"Anyone planning a journey between Christchurch and Picton should always check www.nzta.govt.nz/p2c, or call 0800 4 HIGHWAYS (0800 44 44 49) before travelling to check which route is available and is most suitable for their trip," Forrester said.
There is also surface flooding in many places across South Island towns, rural roads and highways.
The NZTA is asking drivers to slow down, watch for flooding signage or water on the roads, to leave longer following distances between cars and to drive with care and patience.