Tropical air and all its moisture moves off mid-week but MetService warns there is a lot of rain to come before it departs. Then a cold front ushers in wintery weather.

The feed of air from the tropics which brought warm temperatures to New Zealand and heavy rain to western and northern areas over the past week is set to depart.

However, before it moves away an intense period of rain and thunderstorms is expected to move quickly across Aotearoa on Tuesday, affecting already sodden western and northern areas of both islands.

'The band of rain is currently lying over the West Coast of the South Island. It will reinvigorate today into a very active system so when it moves back across the country today it will bring a burst of very heavy rain to those same areas that have been affected over the last week, ” says MetService Meteorologist Jessie Owen.

Heavy Rain Warnings and Watches are in place for northern and western parts of both islands, the same places which have already seen large accumulations of rain over the last week.

A Severe Thunderstorm Watch has been issued for Northland, and Auckland and the Coromandel Peninsula will come under thunderstorm watches as well.

People are urged to stay up to date with the watches and warnings here bit.ly/AllWarnings which are updated routinely every day mid-morning and in the evening.

The rain band will be moving quicker this time around, so most regions will only see a few hours of wet weather.

It will however be very intense rainfall and there is the potential for localised torrential rainfall rates with thunderstorms.

'This very heavy rain will be falling on already saturated ground, so impacts such as surface flooding, rising rivers, and slips are likely.”

Following the exit of the tropical air, a low-pressure system from the Tasman Sea and a cold front southwest of New Zealand both reach the country on Wednesday.

This drops temperatures significantly as far north as Kaitaia, and brings further rain and strong winds, as well as snow to low levels.

Snow is expected to lower to about 400 metres over the South Island on Wednesday, and about 800m over the central North Island on Thursday.

'This colder air is expected to spread right up the country, bringing a distinctly wintery feel. Wellingtonians should only expect a maximum of 10°C on Thursday, five degrees lower than the expected low of 15°C overnight Monday.”

This will be a very noticeable change after a mild start to the month.

Image: MetService.