Those attempting the Routeburn Track over winter months are warned alpine experience is essential because staff and bridges are temporarily pulled from the southern walk.
The Department of Conservation says the route is now outside the Great Walk season and reduced facilities and additional hazards face trampers from April through to October.
"Walking the track during this time should only be attempted by fit, experienced and well-equipped people," the Department of Conservation website advises trampers.
The 32km southern walk normally takes three days to complete.
Bridges are removed to avoid damage from avalanches and there are no rangers based at the huts. There are also no emergency radio facilities for those using huts.
There are four alerts at present issued by the department covering the track.
It includes one in mid-July for snow and ice in alpine areas and warns extreme care is required.
The warning also says alpine skills are essential including walking with ice axe and crampons and using an avalanche transceiver, probe and shovel.
The track is posted with danger signs at present alerting trampers that extreme winter conditions may hamper passage across the popular southern route.
"The winter environment in Fiordland is very cold and wet, with snow and ice common in high areas. Deep snow often hides the track markers."
It warns that alpine equipment and avalanche skills are essential.
Hazards include the track buried in deep, unstable snow, avalanches, thick ice on tracks as well as freezing hypothermic conditions.
Outside the season bookings are not required and huts and campsites are on a first come, first served basis.