Mt Whitney Zone Forums General Discussion August lightning- advice for noobs?

So 5 yrs back when I did the day hike in end-Jun, I reached the top around 2 or 3 in the afternoon and the sky was clear.

It seems that during August, that "late" at the top is risky due to lightning? I know the obvious basics of what to do when static/lightning and dark clouds are seen, but how does one know if clouds forming in the afternoon are benign?

For example, how to know if "typical" afternoon clouds are a hazard?