I agree with everything above, but to add a bit of perspective - not every year is a monsoon year, as they only occur occasionally. The southern Sierra is notoriously stable, to the point where some experienced hikers don't carry a tent during July during a stable year. However, know before you go whether it's a monsoon year, and get be on top of weather forecasts right up until you hit the trail. Given the nature of the trail, it's sometimes impossible to see a storm cell coming much in advanve unless you're above Trail Crest, at 13,600. So, if there's a chance of storms in the forecast, be very cautious.
In a typical year, the odds are rather good the weather will cooperate at the end of July.
