We are facing extended periods of heat without the relief of monsoons. Combined with decreased air quality from smoke and area fires, it is important to monitor your horses carefully for signs of heat stress. Monitoring the heat index before a ride is a valuable tool, especially during the heat of the day or on prolonged trail rides. If the combined heat index is over 130, watch your horse carefully for signs of heat stress. The heat index is calculated by taking the total ambient temperature and combining it with the humidity.