Cattle deaths are mounting in the central U.S. amid a recent heat wave, with early estimates totaling several thousand head.

The extended severe heat and humidity this month have taken a heavier-than-normal toll on the U.S. cattle herd, which typically experiences some heat-related deaths each year.

Daytime high temperatures in North and South Dakota and the upper Midwest have been in the upper 90s to 100 degrees Fahrenheit, with high humidity levels pushing heat indices above 120 degrees in some areas. The severe conditions are expected to moderate over the next week, but temperatures will still be hotter than normal, said Mike Tannura, a meteorologist and head of T-storm Weather in Chicago.

The losses will hit individual feedlots the hardest, since slaughter-ready cattle are worth about $1,300 a head. The deaths, however, are expected to have little effect on overall cattle supplies--and in turn, beef prices--since analysts estimate the nation's total cattle herd at midyear consists of about 99 million head. Of that total, around 10.4 million head are being fattened in feedlots.

State officials reported heat-related deaths at some feedlots in the upper Midwest of 150 to 300 head. In parts of Minnesota, the conditions have been the worst that some producers have experienced, as temperatures remain warm overnight, providing no relief for overheated animals, said Grant Crawford, a feedlot-extension educator at the University of Minnesota.

He estimated cattle-death losses in Minnesota at 1,000 head, with the worst losses in the south-central and south-western areas of the state.

In South Dakota, death losses as of Wednesday afternoon were estimated at 1,200 to 1,500 head, state veterinarian Dustin Oedekoeven said.

Some livestock dealers and market managers said overall losses may be considerably larger than what has been reported so far.

States such as Texas and Nebraska, where the largest number of cattle are raised, haven't experienced the same increase in heat deaths. Although the region has been hotter than parts of the Dakotas and upper Midwest, it hasn't had the same high levels of humidity. Still, temperatures in western Nebraska and southward through the Plains will remain warmer than normal, with highs in the mid 90s and 100s, Tannura said.

The larger concern in the southern Plains is a prolonged drought that hasn't shown signs of abating.

U.S. cattle producers have 30 days to report losses to qualify for compensation from a government program that provides assistance for livestock deaths resulting from a disaster.