Why do we sweat and feel uncomfortable when the outside temperature is 97.8 degrees?

M.A. of Reader:

The average internal temp of humans is 98.7 degrees F. Why then do people sweat and feel uncomfortable when the outside temp is 98.7?

-- L.B. of Poway

Skin's big job is dumping all the heat we generate into the surrounding atmosphere. Otherwise, we'd topple over from the internal buildup. The higher the humidity and temperature, the less efficiently our heat-transfer system works. When you're a big lump of hotness, it's mostly your own hot bod you're feeling. You need to get that bod into a cooler, drier place. Scientists believe this also explains the parking situation in Pacific Beach in August.