Adapting Training for Environmental Conditions (Heat, Cold, Altitude)

[b]Environmental conditions significantly impact performance and require training adaptations.[/b]Considerations:[list][b]Heat:[/b] Acclimatization, increased hydration, lower intensity, earlier/later workouts.[b]Cold:[/b] Layering, proper gear, shorter warm-ups indoors, awareness of ice.[b]Altitude:[/b] Acclimatization periods, reduced intensity, increased recovery and hydration.[/list][quote]"Adapt or be defeated by the elements."[/quote]Which environmental factor do you find most challenging for athletes?