In the TV series Blacklist (season 5, episode 21), I've come across the phrase: "Everything in its time and mackerel in August." Actually, this isn't an English proverb but a Greek one. The original proverb in Greek is "Κάθε πράγμα στον καιρό του, κι ο κολιός τον Αύγουστο.". It means "Things must be done in their proper time, not before" (<a href="https://en.wikiquote.org/wiki/Talk:Greek_proverbs#%CE%9A" rel="noopener noreferrer" target="_blank">https://en.wikiquote.org/wiki/Talk:Greek_proverbs#%CE%9A</a>;) or also "Don't cross your bridges before you come to them./Cross that bridge when you come to it."

Funnily, the proverb is wrong as this article indicates: <a href="https://www.protagon.gr/themata/magazine/kai-ton-avgousto-kolios-apagorevetai-afstira-44341199087" rel="noopener noreferrer" target="_blank">https://www.protagon.gr/themata/magazine/kai-ton-avgousto-kolios-apagorevetai-afstira-44341199087</a>;. It should actually be: Κάθε πράγμα στον καιρό του και ΠΟΤΕ τον Αύγουστο κολιός" (...and never mackerel in August) as July to August is its breeding time. The mackerel is fat and tasty in August (and people might be tempted to fish it then) but for sustainable fishing, mackerels should be spared during breeding time.