Officials estimate as many as 1,100 cattle died in northeast South Dakota last week when the heat index spiked at 106 degrees F in Aberdeen.

The combination of several days of 90-100 degrees F temperatures during the day, high nighttime temperatures, no wind and high humidity killed the animals, says Sam Holland, South Dakota state veterinarian.

Reports indicate that most of dead cattle were near slaughter weight.

The risk for losses isn't over. August can bring long stretches of high temperatures.

Signs of heat stress in cattle include:

Dark-hided animals, fleshy animals, or animals with histories of respiratory disease are at most risk, say SDSU Extension Veterinarian Russ Daly and Extension Beef Specialist Cody Wright.

Heat stress symptoms peak in the early evening hours after the animal's body attempts to regulate its temperature and fails. You should take steps to intervene before severe signs manifest themselves.

In severe conditions, the only option may be spraying the animals with water to cool them rapidly. Even short periods of spraying may be of benefit and should be done before animals begin to show severe effects.

Sprayers or misters are effective means for cooling animals, especially hogs and dairy cows. Too fine a mist will only add humidity, so large droplets on sprayers set to cycle on and off are the best choice. They give animals a chance to cool using evaporation as well. Sheep should not be sprayed, as wet wool prevents the skin from cooling.

Provide shade and extra water, such as supplemental tanks, to pasture or feedlot animals.

Avoid moving, processing, hauling, or otherwise handling animals in hot weather. If these actions are unavoidable, do them very early in the morning.