A good lesson for trampers the world over. Be prepared for anything.

I am more prepared for emergencies than I used to be when going bush.

I once got criticised by a rescue official for leading a party on a mountain, unprepared for an overnight stay.

We would have been down by mid afternoon had we not stopped to help an overweight American who was semi-conscious and had no water container with him. This was the same official whose team cut the cords on our bush stretcher which could be manned by four on each side, strapped him into their stretcher which could only be carried easily by two and awkwardly by four. Then he asked us to carry on taking him down the hill as his team was exhausted from rushing up the mountain to meet us.

I was not impressed. However while I do not always carry cord to make a stretcher I do carry extra water protection, a torch and first aide kit.

NZ's DOC website (Dept. of Conservation) would have been helpful to them, if they had read it and heeded its advice. It's a useful site.
http://www.doc.govt.nz/parks-and-recreation/tracks-and-walks/central-north-island/ruapehu/tongariro-alpine-crossing/plan-and-prepare/

There is no such thing as bad weather - just wrong clothes.

Be outwardly optimistic and inwardly pessimistic.