I've had two patients die in 2 days with symptoms of Heatstroke. One was a 7 week old chihuahua and a 6 year old beagle. And they both were in pens with some shade, and water.
The chihuahua did make it in, but it is a little like trying to unscramble an egg, and he later passed away that evening. I suspect a few other calls have been from heat exhaustion.
Georgia is having a record heatwave this week. The high temp yesterday was 101 breaking a record from 1980. Tomorrow is supposed to be worse than today. This post goes all over, so if your pet is in a similar situation, it is better to be safe than sorry, and don't leave them outside in the extreme heat of the day.