Welcome to WhitneyZone, Catalyst.
Checking the
unused permits pages, last fall there was a major snow storm Oct 4. In 2010, it was Oct 5, with a major rescue after the second storm Oct 18. Snow on Oct 12, 2009.
Checking the
USNavy civil twilight site, on Oct. 1, it gets dark at 7 PM, dawn at 6:30 AM. So you will have a lot less daylight.
I think I'd try for no later than the end of September, based on snow storm records.
Also note that the Mt Whitney trail is closed Sept 4 - 13 (but open Sept 8 & 9).
