RenRev,

I've day hiked Whitney in mid to late October numerous times. I have worn both hiking boots and trail runner shoes for the day hike up Whitney. I do prefer trail shoes any day, and as of late, my preferred hiking shoe. That being said, Whitney in October can throw some crazy cold weather at us. A few years back, I wore trail shoes (gtx) in late October and it was super cold. I climbed Mt Muir on the way to Whitney early morning and it had to be at least 18 degrees, but my feet were fine - did not get cold at all. I had my gators on, really good hiking socks, and the gtx probably helped my feet stay warm as well.

I would say that as long as you keep moving you should be fine. Or just get the Gtx version of the trail shoes.