A record temperature has been reached this afternoon in the South Island as the scorching weather continues.
The official temperature reading at Invercargill Airport was 32.3C at 5.30pm, which MetService said was likely to be a new record high.
Since 1905 the city's January temperature has only reached 30C 14 times - until today.
Temperatures have soared around the country today with central Otago taking the title of the hottest place and reaching 32.5C at 3pm.
And the good weather is expected to hang around for the next few days before it gets muggy and wet later in the week.
MetService meteorologist Stephen Glassey said Millers Flat reached 32.5C, Balclutha 32C and Lumsden and Alexandra peaked at 31.9C and 31.6C respectively this afternoon.
"One of the interesting things is the warmest temperatures are at the bottom of the country in Southland and Otago. It isn't unusual in these northeast flows but it is counter intuitive to what most people think.
"That's the warmest area down the southern South Island at the moment. Invercargill also got up to 31.1C."
Lower Hutt also hit 30.7C and Palmerston North reached 30C this afternoon. Masterton was basking in 29.7C, Hamilton 27.8C and Auckland 27.5C. It was slightly cooler in Tauranga and Whangarei which only reached around 25C thanks to the sea breeze.
Possible thunderstorms were forecast this evening for inland parts of the North Island around Gisborne, Hawke's Bay and southern Taupo, although nothing like yesterday's severe weather.
"It usually coincides with the afternoon heating so we've already seen some pop up at the moment over the Taihape/Southern Taupo are so there could be more this afternoon," Glassey said.
Glassey said the weather would remain fine and warm for the next few days, but warned muggy, wet weather was on its way from Tuesday night or early Wednesday.
Weatherwatch analyst Phil Duncan had earlier predicted that hottest part of the day was still a few more hours away.
"Incredibly, tomorrow may be even hotter in parts of Southland and Otago as the dry airflow continues."
The North Island faces a different type of heat as humidity brings "thicker air", making lower temperatures feel hotter.
"Humidity levels aren't extreme but it's making temperatures in the mid to late 20s feel more like 30," Duncan said.
Many areas in the upper North Island will have overnight temperatures in the 20s.
MetService spokesman John Crouch says the combination of another warm humid day and light winds will lead to cloud build-ups, and this could result in scattered heavy showers and thunder.
"Some of the thunderstorms may severe with localised downpours of 20-40mm/hr and small hail," Crouch said.
"Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips."
Motorists are being warned of hazardous driving conditions and poor visibility in the heavy rain.
"The thunderstorm activity should die down by 9pm this evening," Crouch said.
A deep low pressure system moving over New Zealand is also expected to bring rain and wind across most parts of the country this week.
Today's weather forecast
Auckland and the upper North Island can expect a fine and cloudy start, but showers, possibly heavy this afternoon and evening is expected to hit Bay of Plenty, Waikato and Waitomo.
The humid conditions would also see temperatures soar into the high 20s in Invercargill with a forecast of 28C on Monday.
"A ridge over the country retreats slowly eastwards on Monday as a deep low pressure system over the Tasman Sea moves eastwards," MetService says.
"During Tuesday and Wednesday, the low is expected to move east over New Zealand, bringing rain and strong north to northwesterly winds over much of the country. It is followed by a ridge on Thursday."
Rainfall accumulations reaching "warning criteria" are forecast for Westland on Tuesday through to Wednesday - and likely also for Buller, Nelson and western Marlborough.
MetService said there is also possibility of northwesterly winds becoming severe gale in exposed places of Wairarapa, Hawke's Bay and Gisborne on Wednesday.
"There is low confidence of severe north to northwesterly gales in exposed places of the west coast of the South Island including Nelson and Marlborough and north Canterbury, and in the north and west of the North Island from Northland to Bay of Plenty to Wellington during Tuesday and Wednesday," MetService said.
"But the confidence should increase to moderate for Wellington overnight Tuesday."
Today, it will be mostly fine except for a few showers about the ranges for Horowhenua Kapiti Coast and Wellington.
The forecast is mostly fine also for the rest of the North Island but there may be a few showers mainly inland during the afternoon and evening, some heavy with thunderstorms.
Canterbury and Otago started the day with areas of fog and look likely to end with the same this evening.
Weather this week:
Monday: North Island, cloudy periods with a few showers possible during the afternoon. South Island, Mainly fine in the east, a few showers turning to rain south of the glaciers and Northerly gales in Fiordland.
Tuesday: North Island, cloud increasing with a few showers and possible gale northeasterlies in some areas. Rain developing in Northland late in the day. South Island, heavy falls and cloud increasing in the east, and rain forecasted in the west. Northeasterlies rising to gale is being forecasted for the coasts.
Wednesday: Heavy falls north of Taranaki to East Cape, easing to a few showers. Strong or gale-force northeasterlies easing. Rain, possibly heavy in the north and west of the South Island, and showers developing in the south.