Hiking JMT in September / October

Hello everybody! First time post for me. I have been thinking about taking on a through-hike of the John Muir Trail and today I received a permit for September 14. Planning details aside, is this possible so late in the season? I will be hiking solo from Yellowstone and would like to make it all the way to Whitney Portal, but I recognize that the weather can change quickly at altitude, and I do not want to take unreasonable risks. I have been backpacking before, but I have never taken on a trip as long as this. Is this advisable, or would I be better advised to postpone the big JMT hike and to take a shorter hike in late September -- possibly the High Sierras Trail in Sequoia Natl Park? Thanks! Sara