Sam,
One day in mid-June, I read the NWS forecast for the Mt. Whitney area...no rain for days. As I was head down the PCT from Cirque Peak out on the horizon were rain clouds that according to forecast should not have been there. They dumped a goodly amount of rain on us.
The only thing predictable about the Sierra weather is its unpredictability.
Go, when you plan to go. Bring the right clothing and go as far as Mother Nature and your clothing allow you to go.
