A ferocious blast of thunderstorms, rain and snow will smash the South Island this weekend, with smoke from the Australian bushfires also potentially smothering the country.
The South Island's West Coast will be the focal point of the incoming weather's wrath, forecast to be swamped by more than 300mm of rain over the next few days.
NIWA says the deluge will "elevate the risk of flooding as well as the risk of slips".
WeatherWatch is also warning of thunderstorms with "stray hail showers" expected to hammer the South Island until late Sunday before moving "widely" across the North Island. It does, however, say that the thunderstorms may be "a bit hit and miss".
The large storm that hovered off New Zealand this week is "weakening", according to WeatherWatch. But it is now expected to move over the country, whipping up blistering winds. Gale force gusts of up to 80km/h will pester regions around the Cook Strait from the north-west on Sunday, while westerly winds will hit coastal Southland on Monday.
Of concern for those with asthma and allergies, however, may be a huge incoming "pulse of smoke and dust".
Thick smoke has smothered Sydney over the last day after bushfires flared up in New South Wales. The storm between New Zealand and Australia is forecast to blow that over to Aotearoa on Friday and Saturday.
"Those suffering from asthma and allergies may be affected by the smoke in both Australia and NZ and closing doors and windows may help," WeatherWatch says.
As of Friday morning, aqicn.org - which measures air pollution - says the only Kiwi centre with a "moderate" amount of pollution in the air is Auckland. Everywhere else is deemed "good".
"But Australia is far worse with air pollution levels at some locations now deemed as 'very unhealthy' as the fires continue to burn. This has not changed as the fires continue to rage," WeatherWatch says.
That new airflow will also drive temperatures down. But as WeatherWatch explains that is only expected to reset "most regions back to 'normal' daytime highs" after a very warm week.
"There will be a few places colder than average on Monday but it's short lived with warmer winds returning by Tuesday in the South Island at least. Overnight lows will be below normal for a couple nights too," the weather forecaster says.
Residents on the West Coast should also prepare to see snow on mountain peaks, with 100cm forecast above 1500m until Monday morning. Southland may see 30cm of snow above 1000m.
