I'd say that weather isn't typical but it isn't that uncommon either and certainly not crazy.
Coming down toward the Portal one September we saw almost everything you would need to hike whitney. I wish I'd taken photos of it all. There were hats, a shirt, a sweater, shorts, pants, underwear, two pairs of socks, shoes and boots, a water bottle and two perfectly good hiking poles. These items weren't together. They were in various unrelated locations between Trail Camp and the Portal.