This idiom means to take advantage of favorable conditions or opportunities while they last, as farmers make hay in sunny weather before rain. It conveys urgency or opportunism, often used in personal, professional, or financial contexts to urge action. The phrase carries a tone of wisdom, practicality, or encouragement, reflecting cultural values of timing and the human tendency to seize moments. Its agricultural imagery evokes a fleeting chance, resonating in scenarios like markets or deadlines. The idiom promotes proactive gain, making it a rustic metaphor for seizing opportunity.

The phrase originated in 16th-century England, tied to farming proverbs about haymaking, with its earliest recorded use in John Heywood’s *Proverbs* (1546) as ‘When the sun shineth, make hay.’ It gained traction in 18th-century literature, notably in Samuel Richardson’s *Pamela* (1740). The idiom spread through rural and moral tales, amplified in the 19th century by *The Times* for economic opportunities. Its adoption across English-speaking cultures stems from its vivid imagery and universal relevance to timing, especially in the U.K. and U.S.