Things would turn nasty on Thursday as the ex-tropical cyclone moved in, bringing Northeasterly winds which could develop to gales.
Showers would turn to rain during the day, and by evening the rain could turn heavy, lasting until Friday morning.
"Winds will change to southeasterlies then will ease"
The West Coast of the South Island would bear the brunt of the tropical weather system.
"The low-pressure system itself it will skirt the west of the North Island and cross Westland, the strongest winds and heavy rain will be on the west of the South Island."
This meant Nelson and Kapiti Coast would see large amounts of rainfall and strong winds.
There was a possibility for coastal inundation in those areas, which would be compounded by a king tide.
MetService would likely issue warnings for heavy rain and gale-force winds for the west of the North Island
"It is also likely there will be snow on the mountains.
"It's going to hit the entire country, most places will get rain."
For the South Island Tuesday looked again to be hot with temperature in the mid 30s.
Alexandra in Central Otago was to be the hottest with a predicted 35C, but that could rise a few degrees, Mercer said.
"I don't think 40C is likely but it is not out of the realms of possibility."
Ashburton in Canterbury could hit 33C and several other centres on the east coast of the South Island would likely exceed 30C
The forecast followed a scorching day for many, as Cromwell topped the list with a scorching 36.6C, Pukaki in South Canterbury recorded 34C, Alexandra in Central Otago struck a balmy 33.8C and Palmerston North was the hottest in the North Island at 32.7C.
Yesterday Kiwis across the country sent in some of their own temperature readings to the Herald with some readings exceeding 40C.
At John Selkirk's house in Waimauku the temperature was nudging 42C, according to his thermometer.
Sue and Bryce Hunt's house in Glen Oroua, southwest of Palmerston North, was close behind. The temperature in the shade was 31.7C - while in the sun it was a baking 39.6C.
The couple have been inundated with flies in the last two day, Sue said.
"I went to one of the Countdown supermarkets in Palmerston North this morning to buy fly spray and the shelves were practically empty ā there were six cans left!!"
While it was just shy of 40C at the Hunts' house, MetService meteorologist Lisa Murray cautioned that sunshine and building heat would have pushed the reading well above the real temperature - which MetService had measured at 29C at Palmerston North Airport.
