Thunderstorms and hail are possible for the Auckland region on Friday as New Zealand prepares for a miserable first weekend of winter.
WeatherWatch says heavy rain on the West Coast of the South Island will clear on Friday, as the main front moves to the North Island.
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A cold change which arrived on Thursday in the lower South Island would cover the entire country by Saturday morning.
"On Friday some of these isolated thunderstorms move into the western North Island too," WeatherWatch says. "The cold front advances northwards and mixes with the warmer than average airflow that is being pushed away from northern NZ."
WeatherWatch says heavy snow may impact state highways and alpine passes across the South Island in the next couple of days.
Travellers on the West Coast are being urged to avoid the Buller Gorge with roads closed due to flooding.
Surface flooding, rockfall and slip, snow and wind warnings are in place across many other South Island roads. Snow and ice have impacted the road from Te Anau to Milford.
MetService meteorologist Peter Little said temperatures in the South Island will remain in single digits on Saturday.
"North Islanders will notice a chill in the air over the weekend, with daytime highs around 5C cooler than today [Thursday]."