Late August is probably the best time of the year to hike Whitney. Snow is gone by then and too early for new snow. I've always started by 2:00 am for many years (usually early September) and thunderstorms have never been an issue. Always at the summit by 10am. A couple of times got rain on the way down and a few thunderstorms, but the summit's in the bag and we're well out of the danger zone.
