The saying “dog days” is related to astronomy, and how a certain star appeared in the sky during the warmest months.
edit: Maybe we can consider all Fridays cat days?
It being Frigg/Freya’s day, and Freya is known for her 2 kitties.
IIRC, the “dog days” are when the “Dog Star” Sirius rises before the sun does.
There are three feline modern constellations: Leo, Leo Minor, and Lynx. They’re adjacent, so they’re all visible around the same time.
Leo’s heliacal rising from mid-northern latitudes is around early September. Alternatively, it is most easily visible in the evening in early May. So either early May or early September could be considered the “cat days”!