WEATHER & FLYING CONDITIONS
There are very strict flying rules and regulations when flying around the mountains in helicopters. This is especially more so during the winter ski season - end of November to early May. Many helicopter flights during these months have to be cancelled due to bad weather conditions.
These bad flying conditions can vary from low lying cloud, snow and even rain. It is also possible that even when the weather is perfect at your departure helipad the weather at the destination Helipad affects the flight.
Please see: Bad Weather - Contingency Plan