It's not. This is just an aberrant weather pattern. No doubt my ex, an atmospheric scientist, could provide a more detailed (probably excessively detailed) explanation.
That sounds a lot like mid-Missouri. My sister and brother-in-law, who were living in central New York at the time, came to visit, and I cautioned them about the heat index (that combination of temperature and humidity you mentioned). My brother-in-law scoffed, "What's a heat index?" He learned that lesson pretty fast, because when the arrived the heat indes was something like 114. 
I hope Atlanta cools down a bit!
"It's not the heat, it's the humidity". That's a partly valid phrase you may have heard in the summer, but it's actually both. The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature. This has important considerations for the human body's comfort.
When the body gets too hot, it begins to perspire or sweat to cool itself off. If the perspiration is not able to evaporate, the body cannot regulate its temperature. Evaporation is a cooling process. When perspiration is evaporated off the body, it effectively reduces the body's temperature. When the atmospheric moisture content (i.e. relative humidity) is high, the rate of evaporation from the body decreases. In other words, the human body feels warmer in humid conditions.
The opposite is true when the relative humidity decreases because the rate of perspiration increases. The body actually feels cooler in arid conditions. There is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (decrease), the heat index increases (decreases).
The optimal conditions for human comfort are 23C (approx 75F) and 50% Relative Humidity (Humidity is measured as a percentage to 100%, which is saturated air).
When designing HVAC for commercial building (such as offices etc.) this was design conditions aimed for.
In my experience though even when that condition was achieved some women would be too cold and some men too hot.
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Topic: What's the weather like in your country or state? (Read 346369 times)