make hay while the sun shines

/M EY1 K EY0 W AY0 L DH AH0 S AH0 N SH AY0 N Z/
verb
  1. 1

    To make hay during favourable (dry) weather.

  2. 2

    To act while an opportunity exists; to take action while a situation is favorable.

Source: https://en.wiktionary.org/wiki/make%20hay%20while%20the%20sun%20shines