“Making hay while the sun shines,” which sounds like a euphemism for getting it on in the daytime, actually means to make good use of an opportunity while it lasts. In the days before modern farming equipment, farmers literally had to “make their own hay”: they had to cut, dry, and gather it by hand. Hay is ruined if it’s wet, so if the day was hot and dry, well, you gotta make hay while the sun shines.
Two farmers each owned 40 acres of alfalfa. One farmer said to the other, “I’m going to mow my alfalfa today and let it dry into hay and then bale it.” The other farmer said he was going to wait for two weeks to let the alfalfa grow a little bit taller. The first farmer said, “You should get it done now before it rains.” The other farmer said he would let it wait.
The first farmer mowed his alfalfa, let it dry into hay, baled it, picked up the bales and stored them in the barn. The other farmer waited for two weeks and mowed his hay but it rained the next day and for the next two weeks also. His hay rotted in the field and was unusable.
Make Hay – First Story – Management Story