MetService has forecast heavy rain today for Marlborough and parts of Nelson district, and some roads have been closed as a result.
A warning is in place for the ranges northwest of Nelson, including the Takaka Hill until 7pm.
The downpours may cause streams and rivers to rise rapidly. The forecaster warns surface flooding and slips could also make driving conditions hazardous.
The Marlborough District Council will close some roads as a result.
State Highway One south will close from 6pm between between Peketa, south of Kaikōura, and Leader Road, north of Cheviot, as a precaution against potential slips.
Motorists will have to instead take the inland route. The main highway north of Kaikōura will remain open.
About 100 millimetres could fall in places, with another 100mm expected in the next 24 hours.