Serotinal is a term used to describe late summer or early autumn, but sometimes it's nice to change up the language we use. There are several synonyms that can be used in place of serotinal. One option is "autumnal," which conveys the same idea of late summer or early autumn. Another synonym is "fall-like," which is a more casual way to describe the season. "Late summer" and "early autumn" are also suitable synonyms for serotinal. Finally, "harvest season" is another term that can be used to describe the time of year when crops are typically harvested and the landscape starts to take on a golden hue.