Wintry weekend weather that closed roads and forced a mountain evacuation is likely to be followed by more nasty conditions this week.

The biggest snowfall of the year brought blizzard-like conditions to many parts of the country, prompting authorities to shut the Desert Road, Haast Pass and Milford Road.

At Mt Ruapehu, 30 people staying in upper-mountain lodges yesterday had to be escorted down to Whakapapa village and Ohakune after about 30cm of snow fell there overnight on Saturday.

Ruapehu Alpine Lifts spokeswoman Anna McLaren said the "white-out conditions" also meant operators had to close access roads up to the mountain, where remaining vehicles were buried up to their windows.

It wasn't the only dramatic episode on the mountains yesterday: four people who entered an out-of-bounds area in the Hidden Valley at midday triggered an avalanche half a metre deep, but managed to ski out safely.

The New Zealand Mountain Safety Council had put the danger of avalanche at "considerable" at many mountain areas, including Tongariro, Taranaki, Arthur's Pass, Aoraki/Mt Cook, Queenstown and Wanaka.

Elsewhere in the South Island, a surge of cold air delivered straight from Antarctica brought snow to near sea level in the far south and to 200m on the west coast.

The same cold, convective air spreading north also brought a handful of thunderstorms to southern parts of Auckland yesterday, with hailstorms in several areas.

While the worst of the snow was forecast to be over by last night, higher parts of the South Island could expect a few more flurries this week, MetService meteorologist Tom Adams said.

Heavy showers would return to the North Island by this evening, with a high risk of thunderstorms for Taranaki and a moderate risk for Auckland.

While easing winds and clearer skies would make for better conditions tomorrow and Wednesday, a complex low from the Tasman Sea would arrive late in the week, bringing strong northerly winds and rain.

The trough was expected to move over the country on Wednesday and Thursday, with a low to moderate risk of bringing significant heavy rain to western parts of the South Island.

As the rainband crossed the North Island later on Thursday and through Friday, there was a low risk of rainfall hitting warning levels across western areas. In the southeast of the South Island, there was a low risk of significant heavy rain and heavy snow above 400m.

"Although the winds from the north will raise temperatures briefly, indications are that August will be slightly cooler than average -- in contrast to the warm winter we've had so far -- so the next snowfall may not be too far off."

THE WEEK AHEAD

Today: Rain, with snow possible to 300m in Canterbury and 600m in Marlborough. Thunderstorms in the south and west of the North Island.

Tomorrow: Scattered showers then fine in North Island, mainly fine in South Island.

Wednesday: Showers in the north of the North Island, elsewhere mainly fine.

Thursday: Rain spreads over the country.

Friday: Rain for most places.