Heavy snowfall in the Tongariro National Park has prompted a warning about avalanches and snow covered crevasses from the Department of Conservation.

Hikers and climbers above the snowline on Mt Ruapehu, Tongariro, and Ngauruhoe should be aware of hazards they may not be used to.

Alpine hazards which posed risks to inexperienced people now included avalanches and thinly snow-covered crevasses, especially on Mt Ruapehu outside the ski area, thin ice on the higher lakes on Mt Tongariro, and thinly covered holes or warm ground on Mt Ngauruhoe and Mt Ruapehu.

Such holes may contain volcanic gas.

Steep icy slopes on all peaks need to be approached with caution. Alpine equipment and experience, including training for avalanche conditions, are necessary to proceed safely into the higher elevations of Tongariro National Park.

In addition, warm clothing and boots suitable for alpine conditions are also necessary.

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Department of Conservation technical advisor Dr Harry Keys said recent snowfalls were very welcome but would have covered up some crevasses and other holes on the volcanoes.

"Climbers and others risk injury if they do not make themselves aware of such hazards. This includes venturing out over deep water onto the ice covering or partly covered lakes and ponds on the Tongariro Alpine Crossing," he said.

"Falling through the ice on these lakes will quickly chill people creating serious risk of rapid onset of hypothermia. There are no facilities for the rapid rescue essential in these situations."

Meanwhile the New Zealand Transport Agency said a small number of central North Island roads were beginning to open this afternoon but extra care was needed while there was still ice and snow on the road.

Transport Agency spokeswoman, Karen Boyt, said people should drive to the conditions and be ready for unexpected hazards when using the areas affected by heavy rain, ice or snow.

She said the snow would be high along the sides of the roads which would reduce pullover space.

Ms Boyt said the snow would melt slowly so there may be ice and slushy conditions.

State Highway 46 and State Highway 47 Rangipo to National Park are now open but road users are advised to take extra care because of the snow on the road.

State Highway 2 between Opotiki and Gisborne was expected to open to one lane at 2pm today.

The road was closed after a large slip last Friday.

The site will be monitored over the weekend and road users can expect delays of up to 30 minutes as work continued to stabilise the site.

Further updates and the latest information on other roads is at www.nzta.govt.nz/traffic.

MetService road snowfall warnings here
MetService severe weather warnings here