A sprinkler head at Fonterra's Hautapu Coolstore, south of Hamilton, also activated due to the frost.
Other residents in Hamilton's Rototuna and Fairfield suburbs were without hot water until after 10am - some as late as lunchtime - today due to pipes freezing up overnight.
Following a week of shivering cold temperatures and snow, the sun looks set to shine again, before more rain makes its way over the country.
MetService meteorologist Stephan Glassey said most of the country had woken up to fine and frosty weather today.
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"The exception being the east, and south of the North Island there is a bit more cloud, with some isolated showers.
"But predominantly it's fine over most of the country, and that fine and frosty weather will continue over most places tomorrow as well."
Mr Glassey said the next significant weather producing system would arrive late on Tuesday, bringing with it showers to most of the country.
"We've got a front arriving late on Tuesday and then moving over the country during Wednesday and Thursday and that will bring rain to many places."
The front would move slowly eastwards over the country, preceded by a strong moist northeasterly flow, bringing rain to many parts of the country, with some heavy falls in the north and east of both islands.
"Because the wind direction is predominantly north-east rather than a southerly, so it won't be anywhere near as cold," Mr Glassey said.
He said at this stage no snow could be expected at low levels, and the weather was not expected to impact roads across the country.
Today's forecast:
Whangarei: Fine with light winds. High 12C Low 4C
Auckland: Fine with light winds. High 12C Low 4C
Hamilton: Fine with light winds. High 12C Low -2C
Tauranga: Fine with light winds. High 13C Low 3C
Wellington: Cloudy periods, the odd afternoon shower. Southerly. High 10C Low 4C
Christchurch: Fine with northerlies. High 8C Low -5C
Tomorrow's forecast:
Whangarei: Fine spells, a shower or two. Northeast develops. High 15C Low 10C
Auckland: Fine. Northeasterly develops in the afternoon. High 14C Low 9C
Hamilton: Fine, with morning frost. Light winds. High 13C Low 2C
Tauranga: Fine with light winds. High 13C Low 6C
Wellington: Fine with northerlies developing in the afternoon. High 11C Low 6C
Christchurch: High 9C Low -4C
Source: MetService