Motorists travelling on the Napier-Taupo Rd and State Highway 2 (Napier-Wairoa Road) are urged to take care this morning due to a number of slips on both roads overnight.
There have also been slips on State Highway 2 north of Gisborne and roads are down to one lane in some spots.
The warnings after some heavy downpours in the Bay which are expected to last for another next 24 hours.
Metservice Meteorologist Tom Adams said the region would experience relatively warm temperatures over the next day, but heavy rain was a big concern.
"We're actually looking at some mild and even humid temperatures for this time of the year and that's bringing some very heavy rain," he said.
"I think what people need to be concerned about is the heavy rain warning from 8pm tonight until 8am tomorrow morning where 140-200mm of rain could accumulate, especially about the ranges."
The severe weather event is all thanks to moisture being dragged down from the tropics and it will move relatively slowly through the region, meaning rain is likely to accumulate.
Adams said heavy rain events usually move through the region in a matter of hours during winter, but with tropical events, it's a different story.
"On top of that there will be some gusty winds as well, from around 1am to 3pm tomorrow (Tuesday), some south-easterly winds might become severe, so that comes in secondary with the rain, which is going to be a big factor for both Hawke's Bay and Gisborne."
While many won't be surprised by rainfall in winter, Adams said that a tropical weather event was fairly unusual for this time of year.
"You do get these types of tropical systems coming down on the odd occasion, there's a rigid high pressure that moves south in summer and north in winter and that's what generally shields us from the tropics."
"For low pressure to break through this ridge is very unusual, for a global band of high pressure to make it down to our neck of the woods is even more unusual and it's worth paying attention to, because it's going to be quite a significant weather event."
Hawke's Bay Civil Defence Emergency Management Group Manager Ian Macdonald said people can expect surface flooding, slips and possible power outages.
"We're not expecting any significant flooding in our major rivers, but there could be some localised flooding."
"A lot of the heavy rain will fall around the ranges, so it's not going to impact suburban areas too badly."
Macdonald said it was a good idea for people to keep an eye on road conditions as some areas may experience slips due to the heavy rainfall.
"If people are driving the Napier-Taupo road, there may be slips around that area, but it's also good to check the AA or the NZTA websites for live road updates if you're travelling.
The MetService said the rain was due to clear on Tuesday evening with sunny spells predicted for Wednesday with a high of 13 degrees.