Overheating is common in the Summer, and the silly part is that it's easily prevented!
We most often see heatstroke affected animals on overly hot days, who have had either a lack of access to shade or shelter, a lack of available water, or been confined to a hot and/or humid environment. Or all of these.
Brachycepahlic, or squashy-faced breeds are more at risk, as they lack the mucosal surface area in their noses and throats to effectively cool themselves, and also have obstructive breathing which makes it difficult to pant in the first place. And panting is the number one way a dog keeps cool!!
The images above illustrate the signs of heat distress in animals from early to advanced heatstroke. Heatstroke is serious, and often fatal even when treated as some body systems are too affected to recover. There may also be a delay between cooling the animal, and onset of the complications of heatstroke.
If it's really hot and you think your animal may become hot try to provide ventilated shelter and shade, provide multiple water bowls so if one ends up in the sun, the others stay in the shade, or provide ice licks that will melt in the bowls. If possible have them with you in the air conditioning, and don't exercise them until the heatwave is over!! I have seen dogs die who went on their regular run on a 41 degree day! Remember WE can sweat, DOGS CAN'T!
If your dog is suffering from heatstroke, move them to a cool spot and either hose them (don't use ice!), or place a wet towel on them and fan them - keep the air moving around them. If they are able to, give them a drink of cool water and get them to the vet ASAP!
And I KNOW this doesn't need to be said, but don't leave your dogs in cars during the summer - it's a really effective and awful way to kill your dog. Even if you're going to be just a minute, even if the windows are cracked (which makes very little difference to the internal temperature) it's NOT ok, and disaster can happen in as little as 7 minutes