After the very hot start to September, temperatures have become much more fall like and it has recently felt more like fall. The actual start of the fall season is subjective with some claiming 1 September, others claiming the Tuesday after Labor Day, and others the fall equinox date. The featured chart attempts to take a statistical approach to access the date when the trailing 91 day average temperature starts to decrease. This effectively denotes a 91 day period with the warmest average temperature for the year. The middle subplot provides the date each year for Ames that this 91 day period ended. A simple average puts the date at 6 September, which is conveniently when this period ended this year. The bottom plot extends this algorithm then to consider the duration from the end of summer to the start of the winter season (coldest 91 day period). The average number of days is just 85.5, which implies our fall season is about a week shorter than an equitable season should be! There is certainly much variability with some fall seasons shown to last less than 60 days and others over 100!