Why do we feel very hot and humid before rain comes?

Why do we feel very hot and humid before rain comes? A scientist could give a more precise answer but Quora invites us laymen to jump in as well. I live on the U.S. east coast where humid air is the norm. The exhaust from an industry “smoke” stack contains lots of water vapor. The water vapor exhaust rises up a bit then goes horizontal, staying relatively close to the ground. I travelled to the West last summer and watched an industry exhaust stack there. The exhausting water vapor went eerily straight up in a thin wisp and quickly dissappeared into the humidity free sky. If a moisture laden cloud is above, then the air below probably has a higher level of humidity even before the rain falls. Our skin looses moisture constantly as a means of exhausting body heat. If the contiguous air around our skin is humid, then the skin’s ability to exhaust moisture is impeded by that relative warm humidity, i.e., the greenhouse effect. When the air is humid, our body is less able to loose heat. Sort of like a wet sponge can’t hold more water. When the air around us has little or no humidity, our body readily looses moisture and heat; like a dry sponge. That is why we need to drink more water when we are in dry climates. That is why a higher temperature in a dry climate can feel cooler, in the shade at least, than a lower temperature in a humid climate. “It’s not the heat, it is the humidity.”