Snow flurries are also possible to 500m in Dunedin this evening, while Queenstown could be in for a light snowfall as well.
Road snowfall warnings are in place for Lewis Pass (SH7), Crown Range Rd, and Milford Rd (SH94).
Strong and unsettled southwest winds are expected for much of the country tomorrow, with south to southwest gales affecting some coastal areas in the east of both islands.
A large area of south to southwest gales and heavy southwest swell are expected to affect the waters between New Zealand and the Chatham Islands during Monday and Tuesday.
A ridge of high pressure should build over New Zealand on Tuesday, then move eastwards on Thursday as a low pressure system approaches the country from the Tasman Sea.
The combination of the cooler temperatures from the cold southwest winds and the high pressure, which means much of the country will experience clear and calm nights, will cause temperatures to drop dramatically midweek.
Much of the South Island will wake up to around freezing or below 0C on Wednesday, with much of the North Island temperatures dropping to below their average for this time of year as well.
Parts of Taupo, Taumarunui, Waikato and inland Bay of Plenty will be either around 0C or below. A special mention for the Coromandel which will drop up to 6C below their average for this time of year.
Even Aucklanders who boast an average 8.8C for their minimum temperature during June months will feel the cold at 4C.
Today's forecast
Whangarei: Cloudy periods. One or two showers from afternoon. Southwesterlies. High 18C / Low 9C.
Auckland: Cloudy periods with a few showers, mainly from afternoon. Southwesterlies. High 17C / Low 11C.
Tauranga: Fine. However, chance shower from mid afternoon. Westerlies. High 17C / Low 7C.
Hamilton: Sunny spells, but a shower or two from afternoon. Southwesterlies. High 16C / Low 7C.
New Plymouth: Sunny spells but a few showers, mainly in the afternoon. Westerlies, strong at times. High 16C / Low 9C.
Napier: Fine. Westerly breezes. High 17C / Low 5C.
Wellington: Mostly sunny with northwesterlies, but chance southerly and shower late afternoon or early evening. High 14C / Low 8C.
Nelson: Fine. Light winds, southwest developing in the evening. High 14C / Low 4C.
Christchurch: Fine apart from some morning low cloud or fog. Light winds. High 10C / Low 1C.
Dunedin: Cloudy periods with a few showers from afternoon. Snow flurries possible to 500 metres this evening. Gusty westerlies. High 10C / Low 5C.