"The National Weather Service’s 1991–2020 Phoenix climate thresholds show the progression clearly: the average last occurrence of 100°F is October 5, 99°F is October 8, 98°F is October 11, 97°F is October 13, 95°F is October 18, and 90°F is October 30. That makes about October 18 onward the point when the odds shift noticeably away from mid-90s-plus heat, although individual years can stay hot much later."
i'm guessing that lower daytime temps(avg or peak) will translate into lower nightly lows. (unless we have already hit some kind of max for heat islan absence nightime cooling)