MEMPHIS, Tenn. (WMC) -Summer is officially here and we are already talking about heat index values. You see us talk about heat index values on television, but do you know what it really measures and why it can be an important tool for your health?
The hottest months on record for the Mid-South are typically July and August. The normal daily high for both is the low 90s and lows in the lower 70s. The humidity will make these summer month temperatures feel worse. The heat index or “feels like” index will be an important way to monitor whether it is safe to be outside this summer.
The heat index or the “feels-like” temperature is how hot it feels to you when relative humidity is combined with the air temperature. The body is cooled by sweating and on a hot and muggy day, the atmosphere will demand less evaporation of sweat, which will make it harder for the body to cool down.
When it is extremely hot and dangerous to go outdoors the National Weather Service will issue heat warnings and advisories. This is usually the case when the heat index is in the triple digits. For example, on a 96-degree Fahrenheit day with a relative humidity value of 60% gives us a real feel temperature of 116 degrees, which is in the danger category, meaning heat disorders can occur with prolonged exposure or strenuous activity.
The National Weather Service has certain criteria for Excessive Heat Watches and Warnings. For a Watch it means that conditions are favorable for heat indices to reach 110°F due to a combination of heat and humidity. This is usually issued 24 to 72 hours before the heat takes place. A Warning means heat index values of 110°F or higher during the day with low temperatures >= 75°F at night are occurring or imminent, this is usually issued 12 to 48 hours before the heat takes place.
Heat and humidity is nothing to play around with, Heat Exhaustion or Heat Stroke can take place when the extreme heat hits the Mid-South. Make sure to keep up-to-date with the forecast as we move into July and August which is the hottest months of the year.