When the heat starts rising, burros need extra water and shade. We put up a drip hose line around their corral with misters. When the heat gets into the high 90s and the 100s, we mist them and it seems to help cool the area nicely.
Burros are desert animals but they can still get heat stroke. Here are the signs of heatstroke in your burro:
Skin that is dry and hot Pulse and respiratory rates much higher than normal Unusually high rectal temperatures. Around 104 degrees Fahrenheit. When these signs appear call a vet immediately. The burro should be moved to a shady area with fans or wind to provide ventilation. Cool water should be sprayed on the legs of the animal's body to help the evaporation process. Ice packs should be placed on legs and other areas that exhibit large veins on the surface of the animal's body. Veterinarians normally will give large amounts of fluid to the animal and possibly give cold water enemas or drenches if the core temperature is extremely high. The best recommendation is for equine caretakers to know how to identify heat stress symptoms before they progress to heat stroke. Relieving the burro from exercise and cooling the animal's body by fans and shade will help stop the onset of heat stroke. A simple test to determine marginal water loss is the pinch test. When a section of skin on the neck or shoulder is pinched, the skin recoil will be immediate in normally hydrated animals. Dehydration will delay the skin from bouncing back. Another test is the "effective temperature" test, used to help determine the environmental conditions most likely to result in heat-related illness. This test combines ambient temperature with relative humidity. When the sum of the ambient temperature in degrees Fahrenheit and the relative humidity is around 150, you should use caution in exercising the animal so heat buildup doesn't become critical. Most activities involving long or intense exercise should be postponed when figures approach 180. (Of course, at our sanctuary, the donkeys are not worked.) It is also important not to overlook cool-down periods following exercise bouts, even when environmental temperatures are within the normal range. Heat loss through sweat requires convection and evaporation. Air flow is important for convection of heat from the animal's body. The length of cool-down procedures will depend on the amount of work, the environmental conditions and the individual.
The bulk of these tips came from this article at HorseWeb.com.