If it’s late May of an average or mid May of a low snow year, it’s not impossible and might actually has some advantages. This is assuming you can follow a map and are comfortable travelling on snow maybe 1/3 to 1/2 the time. The mosquitos are less, the streams aren’t as high as they are in June or sometimes early July, there are fewer people, and there is no horse poop on the trail yet. You could resupply in Mammoth (easy to get to from the trail) and Independence/Bishop (an extra day’s side-hike, but INCREDIBLY BEAUTIFUL side hike).
For me, it would all depend on when the first of that year’s PCT thru-hikers start through. Being one of the first, you’d have to know what you’re doing and you’d be breaking a lot of trail. But if there are 10-20 thru-hikers pushing through, you’ll have some tracks to follow. In 2008, the first few went through at the end of May, and by early June there were tracks almost everywhere there was snow. For this time of year, and for the reason of tracks, i’d go northbound.
If you’re rescheduling for non-snow season, i’d recommend late August. Fewer bugs.
markv