Austin had 20 days in June with a high temperature of 100 degrees or higher and Hazel and Myrtle were not too happy about it. They spent a lot of time under bushes taking dust baths and I spent a lot of time looking up ways to keep them cool on the Internet.
Most of the websites that provide great chicken info are located in the UK or someplace that sees snow each year, which ain't Austin. After considerable research and conversations with local chicken parents I found that all we can do is provide plentiful and readily available cool water. So my babies had dishes of water placed all over the yard and I often filled them with ice as the sun hit its peek cooking temperature around 5:00 p.m.
Egg production has slowed a lot, I'd say they are averaging four a week right now. For a few days it looked like I had a Bantam living in my coop, finding these little baby spotted eggs, which were still delicious.
I learned that the hotter it gets the less likely the girls are to drink. Seems counter intuitive, but they don't like warm water, which is why the cool water is important.
I also took the mister on my hose and wet some of the yard they decimated, so they had cool moist dirt to sit in on the warmest days. Overall, they seem like very happy chickens and the last few days have only hit the mid-90s, so egg production is ticking like clock work.
Photo of Fireworks Over Lake Austin by Trey Ratcliff @ stuckincustoms.com