The mercury dropped to 4 degrees Celsius in Christchurch overnight, while Blenheim dropped from 18 degrees Celsius at 5am down to 9 degrees Celsius at 7am, Kaikoura went from 17 degrees at 2am to 6 degrees at 5am, and Timaru plummeted to only 3 degrees Celsius.
However, yesterday Christchurch had a high of 29 and Timaru hit 27 degrees Celsius, WeatherWatch.co.nz said.
The southerly flow is expected to reach Auckland by this evening.
"We usually think of highs, or anti-cyclones, as our summer friends that bring hot, sunny, beach weather - but the truth is that a high can also contribute significantly to cold snaps and this is what we're seeing today," WeatherWatch head weather analyst Philip Duncan said.
Cold nights may be in store for the next few nights, but temperatures should pick up on Sunday.
"The good thing about a high that creates a cold southerly like this is that it then comes in the next day and pushes the bad stuff out east over the Pacific Ocean. This weekend we'll see a high rolling in bringing clear skies and lighter winds, but it will be cold to start with," Mr Duncan said.
Slip, slop, slap, wrap
While many parts of the country have experienced a much cooler and cloudier summer than usual, people should still remember to "slip, slop, slap, and wrap", NIWA warned.
Dr Richard McKenzie, principal scientist radiation said UV will continue to reach extreme levels for most of the country over the midday period until the end of February.
"We're talking about UV levels greater than 10. The World Health Organisation recommends people need to use sun protection when levels are 3 and above. UV levels above 3 are being measured for many hours each day throughout the country and this will persist beyond the end of February, so sun protection is extremely important."
SunSmart manager Laurianne Reinsborough said it is not the sun's heat that burns, but UV, so people can still get sunburnt even on cool or cloudy days.
"Sunburn is a big concern because it is linked to melanoma, the most deadly form of skin cancer. Unfortunately, our Kiwi lifestyle and fierce sun have given us the highest rate of melanoma in the world," she said.
"During the daylight saving months, especially between 10am and 4pm, remember to 'slip, slop, slap and wrap' - slip on a shirt or into the shade, slop on plenty of broad-spectrum SPF30+ sunscreen, slap on a hat and wrap on a pair of wrap-around sunglasses."
Motorway maintenance in Auckland
Meanwhile Auckland's motorway network will be littered with detours later this weekend as maintenance work is done.
New Zealand Transport Agency has advised motorists there will be work on the Northern Motorway, the Auckland Harbour Bridge, Spaghetti Junction, the Southern Motorway, Northwestern Motorway and the Southwestern Motorway from Sunday through to next Saturday.
For more information visit the NZTA site.
Auckland Transport is also planning to run more bus and train services on Auckland anniversary weekend on Sunday, although parts of the rail network will be closed for maintenance work. For more details visit the Auckland Transport site.
