Occasional heavy thunderstorms occur during the summer. The dryness makes the warm summers more comfortable. The Glen Canyon Dam also affects conditions on the river. Demand for electricity is generally greatest during the summer. This results in more and larger water releases and therefore higher water levels.
Fishing techniques vary greatly with different water levels.
This may affect your preference of season. The fall months are generally the most popular for anglers at Lee's Ferry. The weather is excellent with moderate temperatures, few storms, and little wind. The high summer water flows from the dam taper off, exposing gravel bars which have been mostly flooded. This provides great opportunities for the flyfishermen.