Wellington and New Plymouth can expect tops of 17C and 18C today with the rain then setting in tomorrow.
Wellington residents will then need to rug up with forecaster WeatherWatch tipping the capital to drop to a wet and wintry 11C on Saturday.
Christchurch can expect a mostly fine top today of 19C, while elsewhere in the South Island the rain has already set in.
Heavy rain warnings are still in place this morning on the West Coast and parts of the high country in Otago, Fiordland and Canterbury.
WeatherWatch is warning of further heavy downfalls and possible thunderstorms in the West Coast on Thursday with the rain likely to cause slips and flooding, meaning motorists should take "extreme care".
It comes after WeatherWatch yesterday warned temperatures could plummet by as much as 10C this weekend as a snowy blast hits from the south.
The forecaster tipped Hamilton will plunge to a daytime high of 12C on Saturday, while the Bay of Islands and Hawke's Bay will fall to highs of 14C and 12C respectively.
In the South Island, Christchurch will fall to only 9C on Saturday with WeatherWatch warning "it gets colder the further south you go".
This will lead to Queenstown dropping to highs on Saturday and Monday of 5C with snow showers.
Dunedin temperatures will fall to only 7C on Saturday with snow down to 400m and hail to sea level.
Queens Birthday traffic:
Commuting around Auckland might be disrupted over Queen's Birthday weekend due to construction work connected to the City Rail Link project.
The areas impacted most are part of Mt Eden and some rail services on sections of the Southern and Eastern Lines.
Buses will replace trains on some sections of the Southern and Eastern Lines due to upgrades, including the construction of an additional line for a third platform at Otahuhu Station, of the Auckland rail network.
Meanwhile, no weekend construction is planned for CRL's Lower Queen St/Britomart and Albert St sites in central Auckland.
Today's forecast
WhangÄrei: Fine apart from morning showers. High 20C, Low 11C.
Auckland: A few morning showers, then becoming fine. 19C, 12C.
Tauranga: Fine, chance morning shower. 19C, 11C.
Hamilton: Showers clearing morning, then becoming fine. 19C, 8C.
Rotorua Showers clearing morning, then becoming fine. 16C, 7C.
New Plymouth: Showers clearing morning to cloudy periods. 18C, 5C.
Whanganui: A few morning showers then fine. Westerlies, strong and possibly gale during morning. 19C, 12C.
Napier: Fine, but chance morning shower. 21C, 11C.
Wellington: Cloudy periods. Strong northwesterlies, rising to gale in exposed places evening. 17C, 14C.
Nelson: Cloudy periods. Evening showers possible. 17C, 13C.
Christchurch: Mostly fine but some cloud and a few showers at times from afternoon. 19C, 11C.
Dunedin: Mostly fine but some cloud and a few showers at times from afternoon. 16C, 10C.