If the forecast is correct, that would be the coldest temperature recorded so far this year in both centres.
In Napier, it would be the city’s second-coldest August temperature since records began in 1973.
Napier’s coldest temperature this year has been -1.8C on July 4, while Hastings reached -1.4C on July 30.
“It’s going to be really cold and very frosty,” Bakker said.
“Keep your woolly socks well to hand is my advice.”
Bakker said a large ridge of high pressure settling across much of New Zealand would allow heat to escape overnight, creating ideal conditions for widespread frosts.
“The clouds normally act like a blanket, keeping the heat in, but all that heat is just going to be escaping straight out into space.”
On Tuesday, Napier’s temperature was unavailable on the MetService website after the city’s live weather data feed was lost.
Bakker said a replacement was being arranged and the issue affected only live observations, not the forecast, which remained unchanged.
He said there was no timeframe for a replacement.
With snow expected on the ranges and higher parts of the Napier-Taupō Rd, motorists were urged to check road conditions and avoid unnecessary travel.
“The road can get icy if there’s enough moisture around, but frosts are slightly less dangerous because they’re kind of crunchy and powdery, whereas ice is smooth and slick,” Bakker said.
The freezing mornings could also pose a risk for gardeners and growers, with frost-sensitive plants needing protection.
Those living away from the coast should also expect colder conditions than communities closer to the sea, which retains heat overnight and provides a slight insulating effect.
With little rain expected after Wednesday and light winds through the rest of the week, Bakker said the days ahead would bring a mix of sun and cloud, with Thursday shaping up as the standout.
“It’ll be one of those beautiful blue-sky, crispy-ground days.”
The cold snap was expected to ease heading into the weekend, with daytime highs climbing from about 13C on Thursday and Friday to about 15C to 16C by Saturday and Sunday, although another frosty start remains possible on Saturday morning.
“There shouldn’t be anything hazardous over the weekend,” Bakker said.
“Just pack sensibly if you’re going somewhere.”