In the time for eating, using, etc.
Morel mushrooms are only in season for a few weeks in spring.
In heat
Source: en.wiktionary.orgPreach the word, be urgent in season and out of season, convince, rebuke, and exhort, be unfailing in patience and in teaching. Paul
I would go to the deeps a hundred times to cheer a downcast spirit. It is good for me to have been afflicted, that I might know how to speak a word in season to one that is weary. Charles Spurgeon
A gift in season is a double favor to the needy. Publilius Syrus
A man without reason is a beast in season. English Proverb
To rebel in season is not to rebel. Greek Proverb
Provision in season makes a rich house. Romanian Proverb