Those of us in the Plains may want an extra application of sunscreen this week. The National Weather Service is predicting spots from Oklahoma through South Dakota to match temperatures in Death Valley, Calif. Following a roasting of the Plains and Mississippi River valley, the east coast will feel the heat later this week.

The National Weather Service issued heat warnings for a block of states from South Dakota to Wisconsin, down to Kentucky and southwest to Oklahoma. The warmer-climate state Nevada and a snip of California also received heat warnings. While important for humans, we want to remind you how important it is for cows.

On page 281 of our April 25 issue, the article Heat hits cows sooner than we thought updated our 50-year-old thoughts on the Temperature Humidity Index (THI) for high-producing cows.

Since we thought this was a very important article, we have saved it as an e-source on our website at: We also have several other helpful e-sources (educational articles) which you can find by going to the bottom of this page under the E-Sources menu.

You can see the new THI chart below – the new stress threshold begins at 68. At 7:47 today in Fort Atkinson, it is 85 percent humidity. At that level, the temperature needs to be only 71 degrees, and cows will be on the cusp of mild to moderate stress.

Unfortunately, it is 81 degrees F, moving us quickly to the lower range of moderate to severe stress. The humidity is set to fall today due to this morning's scattered thunderstorms, but the temperature will rise to 92 degrees F, according to At 1 p.m. with the expected 92 degrees F and 57 percent humidity, the cows will remain with moderate to severe heat stress, and an average rectal temperature of 104 degrees F.

As you may have read in our articles about the farm in the June 2010 or 2011 issues, our new freestall barn doesn't have fans. However, our cows are treated with misters and soakers in the holding pen and as they exit the parlor. Also, our barn has a pretty constant breeze; today's winds should average about 13 miles per hour.

Take a look at the chart and ensure you are doing all you can to take care of your cows; it will help your bottom line. With enough heat abatement in the barn, you might be tempted to turn off the air conditioner in the house and spend a little more time in the barn.

Click on the chart to open a larger pdf file of the THI data.