Napier was 20C on Sunday and 12C overnight, but the polar blast is set to knock the maximum temperature down to 11C on Tuesday and 4C overnight.
"The front will track up across the country, so even in the north of the North Island we're going to see a dramatic change [in temperature]," Bellam said.
"Those warm balmy nights, we're going to see that change. We're in for some frosty weather."
Meanwhile, it was a grey day in Horowhenua yesterday as heavy rain drenched parts of the district, causing flooding, road closures and overwhelming the region's water treatment plant.
Levin had 44mm of rain between 9am and 4pm on Sunday while 340mm of rain fell over a 30-hour period in the Tararua Range.
Residents were told to stay home - and to save water as the treatment plant struggled to effectively treat water for drinking.
A number of roads were closed and Fire and Emergency NZ crews assisted with flooding callouts.
MetService has issued a number of weather warnings for the coming days as an active cold front moved up the country last night to chill the North Island today.
The front would be followed by cold south-to-southwest winds which could reach severe gale strength.
MetService also warned that gale to severe gale south-to-southwest winds were expected to bring bitterly cold conditions across much of the South Island, causing stress for livestock.
Snow was expected to affect many South Island roads and passes, making driving conditions hazardous.
On Tuesday morning, heavy swells are forecasted in Wellington, rising to 6m, before easing to 4m on Wednesday.
