We've had cold weather in both islands this week but a new airflow from Australia on Sunday and early next week means daytime highs will push into the late teens and then low to mid 20s.
Next week New Zealand is dominated by westerly quarter winds.
Thunderstorms and hail with average wind speeds up to 35km/hr are giving Kiwis a wet start to their weekend.
A moderate thunderstorm risk is in place for the North Island with Northland, Auckland, Coromandel and parts of the Waikato potentially being affected this morning, MetService meteorologist Claire Flynn said.
That risk moves to Gisborne and parts of the Bay of Plenty and Taupo in the afternoon. Most of the North Island will be affected by showers.
Vector is aware of the thunderstorm risk and warns this could cause vegetation to be blown into lines and localised outages could occur.
They promise to restore power as quickly as possible to any affected area. In the meantime they advise people to stay clear of fallen power lines and damaged electrical equipment, watch out for falling tree branches as they can cause damage to power lines, turn off appliances at the wall and ensure you have an alternative way of cooking, like a gas BBQ.
The South Island will have showers around Kaikoura and Marlborough that clear up by this evening. Whereas Sunday should be fine for both islands, Flynn said.
"It should be mostly fine just a little bit of patchy drizzle for the central country in the evening."
Flynn said temperatures should start warming up from Monday with Napier and Hastings getting up to 25°C and Timaru and Oamaru scoring up to 24°C
WeatherWatch head analyst Philip Duncan agrees as the warm air flow comes from the Australian desert.
"The air flow is a return to the ones we saw in August and September - tropical air spilling into Australia's desert, then out over the Tasman Sea towards New Zealand.
"It's short lived but will give a burst of warmer weather starting this Sunday and peaking early next week."
Westerlies likely mean a mild week is on the way for most places - but some may still be a little cooler tonight and Saturday.
And most of the country will be staying dry too, with the West Coast the highest candidate for rain or showers.
A large high will push in from Brisbane to near Cape Reinga in New Zealand, helping encourage a dry week for the North Island and more west to north west winds for the South Island and Wellington region.
Main centre forecasts
Whangarei Showers with a chance of thunder and hail, clearing in the afternoon. Fresh southwesterly winds and a high of 17°C.
Auckland Showers with a chance of thunder and hail, clearing in the afternoon. Strong southwesterly winds and a high of 16°C.
Hamilton Showers with chances of heavy rain and hail, clearing by the evening. Fresh southwesterly winds and a high of 16°C.
Tauranga Showers with chances of heavy rain and hail, clearing by the evening. Strong southwesterly winds and a high of 17°C.
Wellington Showers and rain with a chance of hail that will clear in the afternoon. Southerly gale and a high of 12°C.
