Horses that have seriously overheated tend to be more susceptible to overheating in the future. Horses that have suffered a serious episode should have 10 to 14 days of rest with some turnout and a gradual return to work. Most horses adapt to summer weather if given time to adjust gradually. Use a little common sense and keep a close watch on horses for signs of distress. Horses that are overweight and not used to regular hard physical activity are at the greatest risk.
More halter horses suffer from heat stress episodes then do race horses.