There are many more experienced technicians than I when it comes to hiking Whitney, however, I can offer you some basic advice:
1. Welcome to the "season", July begins the thunderstorms followed up by the more serious late July/August 'monsoon' (the usual trough of moist air that comes up from the south.) Any hiking for the next two months brings a higher chance of encountering storms.
2. Conditions are more favourable for storms from 1pm+ so an early summit lessens the chance of an encounter.
3. Thunderstorms higher up can mean flash floods down below, so an early summit does not necessarily get you out of the woods as far as trouble goes.
4. Your most powerful tool is common sense; if the sky is forming up, chances are that a decision should be made early on -- not after the hail begins to fall.
5. A desirable "Plan B" makes it so much easier to bail (rather than obsessing about all the lost time, money, effort, yadda, yadda, yadda)
6. The best "Plan B" I ever implimented -- aborted SF Bay Kayaking trip -- was sitting in a restaurant overlooking the bay and watching the consequences of everyone else's bad decisions (whilst I ate chowder and sipped beverages)