People are being warned they are risking their lives if they tackle the Tongariro Crossing unprepared as the first winter weather of the year kicks in.

Tongariro Alpine Crossing Source: Getty

Police and rescuers LandSAR have already rescued several people off Mt Tongariro in the past two weeks. That includes a party of six adults and a two-year-old, some of whom were suffering from hypothermia and rescuers said would have died if they did not get to them in time.

With snow forecast down to 700m this week, Senior Constables Barry Shepherd of Taupo and Conrad Smith of National Park Police warn: "If the weather is not favourable, do another activity, don't risk your life.

"If it's raining and cloudy down low, it is likely that the scenic views will be obstructed, and it will be wetter and even colder at altitude."

They are concerned some people do not understand the weather risks associated with hiking in an alpine environment and said the 19km Tongariro Crossing "is not a casual walk in the park".

As an alpine crossing in a volcanic environment, it requires a high level of fitness and understanding of weather conditions.

The Department of Conservation will be recommending visitors go with a guide in the winter season.