New Zealand’s spring will swing between weak and strong westerly airflows, Blue Skies Weather forecaster Tony Trewinnard says.

A cold change on Thursday brings four or five days of southwesterly airflow and frosty nights that threaten grapes and fruit trees.

“We’ve seen bud burst in a lot of grapes and vineyards around the country, so they’re starting to become vulnerable,” Trewinnard says.

From the middle of next week, a strong westerly airflow sets in for about a week with rain for the West Coast and unsettled conditions in Southland and Otago.

“This is going to be a fantastic spring season for grass growth pretty much everywhere.”

The southern South Island faces a colder, wetter summer under El Niño.

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