"It looks like this showery south-westerly flow ... is bringing quite low temperatures," he said.
"Behind this flow is a high-pressure system which will clear out the skies, the weather is going to be very settled, but with that, the temperatures will remain quite low."
James said the region would have to withstand the low temperatures for the rest of the week and there was more cold weather for the weekend.
"It's not looking good unfortunately. There's going to be a few showers around the coast, but they will be more predominant around the Mahia area, rather than Hawke's Bay."
"Looking out, there's not going to be many overnight lows over 4 or 5 degrees, so winter is truly here."
Motorists are warned about the effects, too.
"The Central Plateau will experience snowfall, dropping to about 500 metres, so both the Desert Rd and Napier Taupo Rd will have snow and ice," Metservice Meteorologist Mark Bowe said.
The New Zealand Transport Agency advised drivers, and those planning to travel, to keep an eye on the NZTA social media pages for live updates on road conditions.
Media manager Dan Parker told drivers to take care in shaded areas caused by high banks and tall trees, where roads freeze over and ice may not thaw during the day.
"Frost is more severe at daybreak, so be prepared for this. While it may not be frosty at 6am, it could be an hour or two later," he said.
"There could be winter maintenance vehicles on the highway helping to keep the road open. If you come across any of these vehicles, stay a safe distance behind them and do not pass unless you're instructed to."
Parker said winter maintenance crews were constantly updating highway conditions as closures occurred and conditions changed.
"They have the most up-to-date information and experienced knowledge of their region, so please follow their instructions and advice at all times," he said.