Heat index is the apparent or perceived temperature of the environment and is associated with humidity. As humidity increases, the temperature seems hotter than it actually is. As the heat index rises, the potential for heatstroke increases. In humid environments, it is more difficult for dogs to cool themselves. Use precautions to avoid heat injury, especially when the temperature is over 100 degrees Fahrenheit. Reduce exercise and limit times outdoors. Air conditioning and fans can help keep your pet cool.
For more information, please read the story Keeping your Dog Cool in the Summer.