I was a bit surprised to see quite so many when I was over last August and it was well north of 35°C - you'd think with the water-bottle and sprinkler stations everywhere they'd also throw out a couple of troughs of water for the horses.

They all seemed to be in good health, from what I saw, but horses are pretty finicky creatures - we humans domesticated the horse about 20,000 years ago, breeding the strongest healthiest creatures we could, and they're still a bit shit - and I wouldn't be surprised if a less attentive driver is going to end up killing one.