Thunderstorms and heavy rain are possible for parts of the lower North Island and upper South Island from this evening, MetService says.
The forecaster said a low pressure system over the Tasman Sea would move over central parts of the country from this evening.
MetService meteorologist John Law said the system would bring "wetter weather, especially for the middle parts of the country".
Earlier this week, meteorologists signalled that a change was on the way following sweltering temperatures over the weekend into Monday.
This morning, MetService issued some weather watches and warnings that would take effect from this evening into Thursday.
Marlborough Sounds, Richmond Range and the Rai Valley were all issued an orange heavy rain warning, with 90 to 110mm of rain expected and peak rates of 15 to 25mm/h on Thursday.
"Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible," it said.
"Clear your drains and gutters to prepare for heavy rain. Avoid low-lying areas and drive cautiously."
Law said things were still looking “unsettled” for Thursday, and urged people to check MetService’s website for more information.
Full list of watches and warnings
Heavy Rain Warning - Orange
Marlborough Sounds, Richmond Range and the Rai Valley - 18 hours from 7pm today.
Heavy Rain Watch
Nelson and Tasman Districts north of Nelson Lakes - 16 hours from 5pm today.
Buller north of Granity - 13 hours from 6pm today.
Wellington - nine hours 6am to 3pm Thursday.
Marlborough south of the Richmond Range, and the Kaikoura Coast - 18 hours from 9pm today.
Severe Thunderstorm Watch
Taranaki - 21hrs from 2am tomorrow.
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