Here's an idea:
Build them a temporary wind tunnel.
Here's one way to do this (you can modify this idea to better suit your own situation):
Take a pair of sawhorses and place them far enough apart to support a piece of 1/4 inch, 8 feet by 4 feet plywood. You don't need anything thicker than that, though if you have thicker, it surely will work too.
Now, get a thick, dark tarp -- the kind with holes/grommits in it. Make sure it is at least 12 feet long and wide enough to touch the ground on both sides after you set it up on the plywood. Take that tarp and hang it on the plywood the same way that you would hang a tablecloth on a table, except that you need to have the tarp long enough to touch the ground on three of the sides (but NOT four sides, since you need to leave the fourth side open for the chickens to wander in and out). Take tent stakes and string to secure the two sides of the tarp that run the length of the future tunnel to the ground (that is why you need a tarp with grommits in it). You do this so that the tarp doesn't fly all over the place once the fan is turned on. Alternatively, you could use 2 by 4's to weight down the long sides of the tarp if the tarp is long enough to allow for that.
On one end of the "tunnel" you place a fan -- preferably a rather strong air circulator. Those cheap, plastic, Lasko box fans really don't circulate much air. Lowes and Northern Tools sell good box fans for the job (with metal blades) for about $40 bux.
You will need to place that fan at the end of the wind tunnel that you will close up with hanging tarp.
Put the fan inside the tunnel, but at the end of it, and then turn it on, even though it is not plugged in yet. Because you will need to close that end of the tunnel down with tarp and tent stakes, you want the fan to remain in the on position (and the fastest speed). You will control whether it is turned on or off by plugging the thing into the outdoor wall socket, or else in or pulling the plug out of the outdoor wall socket.
After you put the fan into the makeshift tunnel and then close up the end where the fan is, it is time to run an outdoor extension cord to the fan. Make sure that the point where the fan's cord plugs into the outdoor extension cord is protected from water and rain. If you have no other way to do this, use alot of electrical tape to cover over that union and make it water proof. That's what I do, and it works, as long as I use enough electrical tape to cover every thing up really well. Then I just plug the outdoor extension cord into the outdoor electrical socket built into my outdoor wall, and frankly, I don't even unplug it during rainstorms because the way they designed and built that socket, it doesn't let water in.
Meantime, I can run that fan 24/7 -- even when it is raining -- because the fan itself is underneath the tarp covering, and the tarp covering is tied well to the ground with some wire and tent stakes.
But, of course, the chickens don't need the wind tunnel when it rains. They need the wind tunnel on days like today, when it is 100 plus degrees.
I built this makeshift wind tunnel inside their chicken yard. I put some food and water at its entrance, and then let the chickens decide when they want to go inside there to escape the heat. Frankly, they spent the entire day inside their tunnel today, until near dusk, as it is cooler than their regular henhouse. Other days, when it is not so hot, they don't spend alot of time in their tunnel, as they prefer the sunshine.
When the worst of the summer is over, I'll just disassemble the whole thing. It will take only a few minutes (the most time consuming part of the disassembly will be when I take all that electrical tape off of the place where the fan plug meets the outdoor extension cord). I can then use the plywood for other building projects or save it till next year. I will save the tarp for next year too, while the outdoor extension cord will be used this winter to provide power to the ceramic heater I have in the coop.
