Above freezing is good (so the water doesn't get covered with ice.)
Above freezing is warm enough for the chicks.
Small breezes are fine, but heavy wind is not.
I would try to block any heavy wind, but otherwise keep it as cool as possible, with as much ventilation as possible. So for Monday with a predicted 86 degrees, I would remove ALL the plastic.
As others have said, the mother hen will warm her chicks any time they need itI I can definitely set up blocks to strong or cold winds if they come, while keeping the place well ventilated