Thunder storms, frosty temperatures and tornadoes are likely throughout the week, as mid-winter weather arrives early.
Hail and thunder storms are forecast to lash the North Island in coming days, particularly in the central region: Waikato, Rotorua, Waitomo, Taupo and Taumarunui.
Temperatures are tipped to fall into single digits in the South Island, and to be around the 15C in the North Island.
Tauranga residents yesterday got a preview of what's in store, when a freak hail storm turned the city white, and left many people shovelling ice from their driveways.
Resident Pete Mannington had a front-row seat as the storm struck.
"We were watching a movie and then all of a sudden this chronic noise - thunder and lightning - went off and the TV cut out."
The hail lasted about 30 minutes, leaving everything "dead white", he said.
"The road was covered with ice - like snow.
"We saw a few guys on their boogie boards riding down the sand dunes.
"You wouldn't expect it up here - the hail looked like snow - it was about 30cm thick."
WeatherWatch analyst Philip Duncan said the icy conditions had arrived about two months early.
"This is July weather. Winter has definitely come early, with hail storms, lightning strikes and weak tornadoes."
Stormy weather and heavy rain are forecast for all parts of the country throughout the rest of the week, including the weekend, MetService forecaster John Crouch said.
A high of 14C is expected in Auckland today, though the rest of the week is expected to be a little warmer with temperatures reaching 17C.
Wellington can expect slightly cooler temperatures between 10C and 14C this week, and Christchurch is forecast to have highs of 9C - though the weather should remain fine - throughout the week.
WeatherWatch is also warning of possible tornadoes and water spouts.
Both were reported in the Bay of Plenty and in Warkworth and Orewa north of Auckland yesterday.
In Warkworth, the roof of a home in Westpark Glen was torn off by strong winds.
Other properties in the area lost TV aerials and small trees were uprooted. Power was cut in Warkworth for ten minutes.
In Mt Maunganui, shoppers were evacuated from the Bayfair Shopping Centre when yesterday's hail storm caused flooding and roof damage in several stores.
Police were warning motorists on State Highway Two of ice forming on the road.
Flooding was reported and roads were closed at Mt Maunganui and Papamoa.
Papamoa Primary School students will have today off because of damage to classrooms.
Bay of Plenty fruitgrowers said it was too early to say how much damage the storm had done to their crops.
But Jodi Johnstone, of Trevelyans Pack and Cool in Te Puke, said the damage would be significant.
"The hail in some areas has been decent sized blocks so there will be some damage.
"There's a lot of green fruit to come off the vines - we've got another six weeks to go."
The hail storm was yesterday heading from Tauranga towards Whakatane, but was expected to ease.