On days with extreme heat, expect the water usage to go up even further
During hot summer months, the water needed for a cow herd often determines several other management decisions. To best assess the adequacy of water quantities in surface water or from wells or "rural water" supplies, it first is necessary to have an idea of the amount needed for cattle of different sizes and stages of production that you may have during the summer on the ranch.
A University of Georgia publication lists the estimated water requirements for cattle in different production stages if the daily high temperature is above 90° F. They suggest that amount of water required can be estimated by the production stage and the weight of the cattle.
To read the entire article, link here.