Clear skies produce strong Ultra-Violet (UV) rays and when used near water light is further reflected.
Ultra violet light is one of the major contributing factors that cause fading and fabrics to break down. Here are some simple tips to optimise the life of your curtains:
Always use good quality lining.
Consider the compositions of fabrics; some will fade and break down faster than others.
Sunscreen blinds are recommended
Always allow space for your curtains / blinds to be pulled back off your windows.