Wanaka-based guiding companies Adventure Consultants and Aspiring Guides are completely booked out this month for climbing courses and ascents of Mt Aspiring, Mt Cook and other New Zealand peaks.
"I think people recognise that that's the time of year when the snow conditions in the mountains are at their best," Adventure Consultants owner Guy Cotter said.
The company had already turned away "around $100,000 worth of business" from international clients in November-December because there were not enough fully qualified guides in New Zealand to meet the demand and working with Immigration New Zealand to bring in foreign guides had been "problematical", Mr Cotter said.
Mt Aspiring has been particularly popular with climbers - predominantly Australians - in the past few weeks. Mr Cotter was "amongst the crowd" on a day about a fortnight ago when he understood 22 climbers had reached the summit of Mt Aspiring, the highest number he had personally seen there at any one time.
"It was one of the little spikes you get," he said.
"I guess it just reflects the start of the season and a good weather window."
Despite a dry winter, frequent spring snowfalls had been filling up the glaciers, providing good mountain access.
The snow conditions this year were similar to those 20 years ago, when the mountains were accessible the entire summer.
However, the situation could change quickly if there was hot, dry weather in the coming weeks, Mr Cotter said.
Aspiring Guides director Andy Oxley said the company's pre-Christmas bookings were at maximum capacity and about on a par with the past couple of years.
Department of Conservation community relations manager Annette Grieve said last month's occupancy of Colin Todd Hut - at the base of Mt Aspiring's northwest ridge - was about 160 people, which was also similar to numbers in recent years.