Even with meteorological summer just 10 days away, Kiwis are about to get hit by a southerly change, which will see temperatures plummet.
NIWA says Kiwis can expect another polar jet stream which will see "chilly temperatures for the time of year".
"Just in time for the final week of meteorological spring, a sharp southerly change looks set to move up the country on Friday, leading to some chilly temperatures for the time of year," NIWA said.
MetService said a "burst of cold air" is going to see a "real dramatic difference" in temperatures, especially in the South Island.
MetService meteorologist John Law told Newshub Christchurch is expected to reach 27 degrees on Thursday before plummeting to just 14 degrees on Friday due to that southerly change.
Masterton is also set to see a dramatic change in temperatures, with an expected 25C on Thursday before dropping to 14C on Saturday.
"A real change and that is a change in that wind direction so we go from a northwesterly so you get your classic burn effect wind, where the winds come down and they warm up pretty well," Law said.
"So that gives you warm temperatures... but it's that real change as we head through towards the end of the week, so for Friday, Saturday, we'll find that cold air come back."
But while it will be a "cold one" to end the week, Law said the South Island is the place to be with fine weather on the way.
But it's not good news for the North Island with bad weather to lash the island.
MetService said there is a "moderate risk" of thunderstorms and heavy showers for the Coromandel Peninsula, the Kaimai range, Waikato, Waitomo and the southern and eastern parts of Auckland on Tuesday afternoon and early evening.
The forecasting agency said there is also a "low risk" of thunderstorms for eastern Northland to Rotorua, northern Taranaki and the central high country, where isolated heavy showers are likely.
"Any thunderstorms that occur will bring localised heavy rain of 10 to 25mm/h," MetService said.
Law told Newshub the bad weather will also hit the North Island at the end of the week.
"We are going to find that wet weather transfers up towards the North Island by the end of the week. So for the North Island on Friday, it will be a wet one, particularly out towards the eastern coast," Law told Newshub.
"So for the eastern side of the North Island on Friday and Saturday, more wet weather, very similar to what we've had with that low pressure towards the north-east."
Law said the South Island can expect clear skies on Tuesday except for the far south, with Southland and Otago expected to see some heavy downpours.