Horses are vulnerable to heat stress during work and in poorly ventilated housing, and proactive summer management including shade, water, and modified exercise scheduling is essential welfare provision.
Horse heat stress welfare is an area where management decisions have immediate, acute consequences: a horse worked at high intensity in hot humid conditions can progress to heat exhaustion within minutes, with potentially fatal consequences from hyperthermia. The temperature-humidity combination is more important than temperature alone - horses can tolerate dry heat reasonably well but struggle in humid conditions where evaporative cooling through sweating is less effective. Competition horses are at particular risk when events are scheduled without adequate consideration of weather conditions or without cooling protocols. Horses turned out in fields without shade have no capacity to regulate their thermal environment and may stand in sun-exposed areas if the social dynamics of their group prevent access to shaded areas. Stable design for summer ventilation is a significant welfare factor in hot climates.