ˈdog days noun [plural]

1. the hottest days of the year

2. a period of time when something is not successful:
Few opera houses survived the dog days of the 1980s.

[TahlilGaran] Dictionary of Contemporary English ▲

dog days
the hottest days of the summer.
At times, during the dog days of summer, the stream dries up completely.
(usually + of)

[TahlilGaran] English Idioms Dictionary ▲

dog days
n. phr. The hottest days of the year in the Northern Hemisphere (July and August). (The ancient Romans associated this time with the "Dog Star"
■ Sirius
■ which becomes visible in the heavens at this time of year.)
"The dog days are upon us," John said. "It's time to go swimming in the lake."

[TahlilGaran] English Idioms Dictionary ▲