....Several years ago the Labor Day forecast indicated rain, but then the temperature dropped and the Sierra were blasted with blizzard conditions for four days over that weekend...Cold without much snow can still be deadly.
Yes, even clear skies in September doesn't mean safe weather. We last spent the night at Trail Camp on 9/22/16. Perfectly clear skies, but the temperature that night was somewhere below 15. I found the Cottonwood Lakes temperature link while trying to answer the question: "How cold was it?" (17 was reported). I know that wasn't normal, but be prepared for life-threatening cold, even before 10/1.