Dictionary.net

• Of, pertaining to, or changing with, the seasons; as, seasonal trades.

1919 - The Winston Simplified Dictionary
By William Dodge Lewis, Edgar Arthur Singer

• Pert. to the seasons; in season, at the right time; sufficiently early; out of season, too late; beyond the proper time.

1874 - Etymological and pronouncing dictionary of the English language
By Stormonth, James, Phelp, P. H.