The Department of Conservation is discouraging unprepared trampers from taking on the Great Walks this summer.
Senior ranger Ken Bradley said he had seen increasing numbers of people trying to do the walks with barely any equipment during the past few years.
All walkers should have wet weather gear, suitable footwear, food and cooking equipment, he said.
"They'll walk with a sleeping bag, a very thin one, a pack about the size of what we call 'kindy bags' and travelling on basically a bar of chocolate and two-minute noodles.
"Their wet weather gear is just totally inadequate and a lot of their equipment in their packs, if we have any decent rain, everything just gets absolutely soaked."
Poor preparation was a constant worry for rangers managing the tracks, Mr Bradley said.