Civil Defence wants to remind people to be careful on the roads and drive to the conditions as severe rain hits Hawke's Bay.
Hawke's Bay Civil Defence's group controller, Ian Macdonald, said there may be localised ponding and slips on roads.
"Really the only advice we would give people is to make sure they are prepared if they are travelling in particular, and that they are very aware of the road conditions."
However, he said with the worst of the rain expected in the ranges they were not expecting significant issues with today's weather.
MetService issued a severe rain warning for Hawke's Bay yesterday morning.
The warning covers all of Hawke's Bay excluding Wairoa, and could see up to 120mm of rain in the ranges and coastal hills, with 60-80mm expected elsewhere.
During the worst of the rain, Hawke's Bay could see between 15-20mm of rain per hour, and there is a moderate risk of thunderstorms this morning.
"In the hill country they do get that sort of rain," Macdonald said.
MetService meteorologist Stephen Glassey said the weather was being caused by a complex low pressure system.
"We've got quite a complex low pressure system sort of lingering over the eastern North Island.
"It's going to drive a south, southeast wind into the Hawke's Bay area."
Although the severe rain is only expected for a 22-hour period, from 3am Wednesday to 1am Thursday, the rest of the week is also looking damp for Hawke's Bay.
"The heaviest rain is likely to be Wednesday, but it's still likely to be raining on Thursday, Friday, and even possibly into Saturday as well," Glassey said.
South and southeasterly winds were bringing the cold with them, with highs in the low teens for the rest of the week.
Wairarapa and Wellington's eastern hills were also under a severe rain warning.