In reply to Simonj:
Tuolumne's perfect end of year season is generally around September.
after that, it's a question of how rapidly the storms begin to roll in.
October is often fine but can be colder as Tuolumne is at altitude.
Last time I was there in September, a couple of years ago my water bottle froze solid over night, so prepare for low night time temps in camp but climbing temperatures were on the high side.
It can sometimes feel quite chilly if the wind picks up.
As I said, the farther into October you get the more chance of catching a storm. That storm may well bring a lot of snow that high up, when Yosemite Valley is still hot and dry. At least you always have the option of bailing to Yosemite if there is bad weather up there.
Also, be aware that, if electing to going in September you can only stay 7 nights total in the park, by any means, up until around the 15th. - unless you've learned the Park Warden cat and mouse tricks o the trade!!
If you're going in October there will be no issues there.
Other than that, the climbing in both venues is excellent! Enjoy.