Forecast rain for 8am, Tuesday. Photo: NIWA
An active warm air mass will be "rung out like a sponge" over parts of the country this week, bringing heavy rain warnings, humidity and warm nights.
MetService issued orange heavy rain warnings for the next two days over parts of the North Island including Tauranga, Rotorua and Coromandel and a heavy rain watch over Hamilton, Taupo and New Plymouth.
Some of the South Island's West Coast also received orange warnings with parts of Southland including Te Anau being on a strong wind watch.
Most of the warnings are set to be active from Tuesday and continue to Wednesday.
️ Heavy rain will begin in the western South Island tonight and continue through Tuesday night
— NIWA Weather (@NiwaWeather) November 17, 2025
With high terrain likely to receive 200-300 mm or more in about 24 hours, streams and rivers in the West Coast will rise rapidly and may end up well above normal or extremely high pic.twitter.com/leNCtlBfJp
MetService meteorologist Alec Holden said the rain warnings and watches were due to different reasons for each island.
"For the South Island, we have a very large frontal feature that is crossing the island over the next couple of days," he said.
"Ahead of it, it is directing a large, very moist and warm air mass almost straight from the tropics down over the top of the North Island. . . we're expecting that to be wrung out like a sponge."
The Bay of Plenty was a particular area of concern which currently had an orange warning, but there was a moderate chance of it turning into a red warning.
Although there was no warning set in place for Auckland, Holden said that could change as they were monitoring the area closely.
Heavy rain warnings and watches have been set over parts of the country as a warm air mass approaches the country. Photo: MetService/Screenshot
He also said with heavy rain warnings there was the risk of flooding and in parts of the North Island there was also a risk of thunderstorms developing in the "very energetic tropical air mass".
The warm air mass, which acts similarly to an atmospheric river, would be coming to the North Island from the northeast of the country.
It is set to bring not only rain, but higher humidity and warm temperatures especially at night.
Holden said temperatures during the day would be within the average for this time of year, however, night-time temperatures are expected to be warmer than usual.
"Places like Auckland, for example, they only have like a four degree difference between their maximum daytime temperature and their minimum nighttime temperature over the next couple of days."
Photo: MetService
Tuesday and Wednesday are expected to be wet, but as the system starts to move away towards the end of Wednesday, a ridge of high pressure would give most of the country a "reprieve from the wet weather".
Although heavy rain is forecasted for a majority of the country, Christchurch and the East Coast of the South Island are the places to be.
Holden said warm temperatures would hit those parts of the South Island, but very little rain is expected.
"There's always the chance of something sneaking over, but it looks like they will, if they get anything, they will be quite unlucky."
Earth Sciences New Zealand meteorologist Chris Brandolino said the weather activity forecasted over the next couple of days was not uncommon during a La Niña cycle.
"It's consistent with La Niña, so La Niña has emerged in the pacific and La Niña tends to increase the odds for these types of air flows which increase the odds for impactful rainfall events"
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