Pavement hot enough to cause second-degree burn injury

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TENNESSEE VALLEY (WHNT)-- Excessive summer heat is forecast to continue in the Tennessee Valley into the middle of the week.

Afternoon highs have been warmer than 95 degrees every day since June 15 and 90 or above every day since June 5.

As hot as the temperature has been, you might be surprised at just how hot other surfaces-- like driveways, sidewalks and parking lots-- can get during the afternoon.

The normal temperature of the human body is 98.6 degrees. The National Institute for Standards and Technology says human skin begins to feel pain at a temperature of 111 degrees (think hot bathwater). At 118 degrees, human skin can sustain first-degree burns; a second-degree burn injury can occur at a temperature of 131 degrees. Human skin is destroyed when temperatures reach 162 degrees.

Sunday afternoon, I measured the temperature on various surfaces outside my house: the yard with green grass, the concrete sidewalk and the asphalt parking lot.

Not surprisingly, the blacktop parking lot was the hottest-- a whopping 141 degrees around 2 p.m. Sunday. That's hot enough to cause a second-degree burn injury to bare feet and pet paws. The concrete sidewalk measured 122 degrees, just over the threshold of first-degree burns. The grassy area measured 105 degrees-- about 10 degrees hotter than the air temperature at the time. Various dark metal surfaces were hotter than 145 degrees.

This has a lot to do with something called albedo, which describes the reflectivity of a surface with respect to radiation. Generally, darker objects absorb more radiation and become hotter, while lighty-colored surfaces do a better job of reflecting radiation from the hot sun. This is why wearing lightly-colored clothing is recommended if you have to be outside during extreme or prolonged periods of heat.

Caution should not only be taken during the heat of the afternoon. Even in the morning hours before direct sunlight, places like parking lots and driveways can be 10-15 degrees hotter than the air.

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