The classic ski route from Chamonix to Zermatt is usually done in April and early May. It can be done in March - when we went - if avalanche conditions are moderate.
In 2011, the first crossing was completed in late March after we returned to the states. However, we did some excellent piste and good ski tours. Additionally, Carter Rowley and I managed to make attempts on the Petite Aiguille Verte as well as the Cosmique Arete.