It inevitably will get warmer after Labor Day, but for many or most of us, the average high will be in the low 80s by then. In September, you can be much above average in temperature, yet be below 90. Average highs are starting to plummet. For goodness sake, Greensboro had a high of 79 and lows in th mid 60s yesterday in a “warm and humid air mass.” The lower sun angle and shorter days make it harder to sustain big heat, although sporadic big heat obviously has happened in history.