With scorching temperatures, although the thermometer may say one thing, humidity can elevate the effects of that temperature.

Weather reports typically provide a “feels like” temperature, known as a heat index, which, in the summer, may be higher than the actual temperature. Meteorologists use a combination of the actual temperature and the level of humidity to determine the heat index.

To cool our bodies, we sweat. As the sweat evaporates off our skin, heat is removed, which cools us. When humidity is high, the rate of evaporation decreases. We sweat, but since it’s not evaporating, we don’t cool off.

If internal body temperatures increase, people may experience heat-related stress, such as heat cramps, heat exhaustion or life-threatening heat stroke.

Health professionals recommend people avoid excessive physical activity during times of high heat and humidity and increase their fluid intake.

The National Weather Service has created a chart that shows “feels like” temperatures for high temperatures and humidity, and issues weather alerts when the heat index is expected to exceed 105 degrees for two or more consecutive days.

Lower heat index readings still need to be considered if someone will be outside for long periods doing strenuous activity.

Duane Friend serves as a University of Illinois Extension energy and environment educator.