Days of salads and shorts are about to be interrupted as the country faces the first cold snap of the year.
The MetService warns of snow down to 800m or 900m in the lower North Island and overnight temperatures of 10°C even in Auckland on Monday and Tuesday.
That could cause transport problems on higher roads and put exposed livestock under stress, it says.
Duty meteorologist Mariken van Laanen said last night skies should at least clear over the weekend in the north, but the weather everywhere on Monday was expected to get colder.
"It's going to be the first cold snap of the year," she told the Weekend Herald.
Auckland's high of 23°C yesterday is expected to stay the same today, before falling to 19°C tomorrow and 17°C by Tuesday.
Overnight lows are expected to drop from 16°C last night to 10°C on Monday and Tuesday.
But Ms van Laanen indicated it wasn't time for a permanent change of wardrobe yet as things should warm up again by week's end.
Fellow meteorologist Peter Little warned in a blog yesterday of a polar blast likely to bring snow to 400m above sea level in the deep south and cold, showery weather with hail and strong to gale force southerlies as far north as Waikato.
"The culprit is a deep area of low pressure forecast to move just east of New Zealand on Monday, with a cold south to southwest flow spreading over the country," he wrote.
Mr Little also warned of large south to southwest swells expected to hit much of the country's coastline, with strong winds whipping waves up to possibly 8m to 10m along the east coast on Tuesday.
Outlook
• Whangarei: High 24°C, low 14°C
• Auckland: Morning showers. 23°C, 13°C
• Hamilton: Morning showers. 23°C, 10°C
• Tauranga: Showers 22°C, 14°C