Make hay while the sun shines is a proverb which means that one must make full use of the situations and circumstances when they are favourable.
It is like making good use of the opportunity while it lasts.
It also acts as a reminder that conditions may not remain favorable for long and one must take full advantage without wasting any time.
1. Monsoons not only bring a plethora of diseases along with them but also bring an opportunity for the doctors to make hay while the sun shines.
2. During protests by the local bus drivers in Mumbai, cab drivers usually start charging exorbitant amounts and make hay while the sun shines.
3. As I had some free time today, I decided to make hay while the sun shines and went out with friends to watch a movie.