When it’s cold backstage one has to be careful when filing one’s nails for the performance. Colder temperatures make the flesh on one’s hand contract and the nails stick out more, and therefore seem longer. When the temperature rises, either because of the audience (large groups of people will automatically raise the room temperature) or because the venue uses old fashioned incandescent lights, the flesh of the plucking hand will get fuller and will obscure the nail. Suddenly the nails are too short!