How to protect them from the heat?

Hello everyone!

I have 4 chicks in my backyard.

We got a couple days of hot weather last week with 30°C/96°F and I've noticed that my two black chicks seemed to suffer from the heat, especially the small polish one.

She was hyperventilating and acting very panicky. We tried to keep her in the shades in cool grass and ultimately sprayed some water on her which seemed to help a bit.

I'm worried about the summer, every year is getting warmer and warmer, the temperatures rise above 40°C/104°F at least a couple times a year. (it's very hot for here, I live in Brittany in France). What will happen if 30°C is already having such an effect on them...?

Does anyone have tips to keep them from overheating during the summer?

The coops are set close to trees, and part of their enclosure are covered by a white tarp. The coops themselves are always in the shades but the enclosures are sunny in some places, some parts are more sheltered.