Difference Between Humidity and Moisture

Humidity vs Moisture

People are always confused between the concepts of humidity and moisture as these are closely related concepts. This is because of the use of the word humidity in place of moisture when talking about weather conditions. In daily life, moisture finds many more applications than just weather, and this is what this article will attempt to highlight.

At any point of time, air in the atmosphere contains some amount of water vapor. The percentage of water vapor in the air compared to the maximum water vapor that air can hold at any given temperature is known as the humidity of air. More the humidity, more one feels stickiness in the air, which is because of the moisture present in air. At any given temperature, air has a specific capacity to hold moisture. When moisture content in air surpasses this value, excess moisture spills out in the form of precipitation. However, precipitation can take place by lowering the capacity of water retention by lowering temperatures also.

So, if moisture in air is half of the capacity of air to hold water, the relative humidity is 50% and if it goes up to 3/4th of the capacity of air, we call it as 75% relative humidity. Water content remaining constant, relative humidity goes up or down with variations in temperatures. Increasing temperature will lower the relative humidity while decreasing temperatures will increase relative humidity. The best example of this concept in daily life is the presence of dew on grass in your lawn in the morning. At night, temperatures go down causing relative humidity to go up making excess water present in air to spill over in the form of condensation that is seen as dew on grass and the wind shield of your car.

There is another thing that baffles people and it is the distress or feeling of discomfort with increasing humidity. Let it be clear that both temperatures and humidity are responsible for the feeling of discomfort. If temperature goes down bringing relative humidity to high levels, we start feeling discomfort despite air being cooler which confuses many. Again, temperature being in the vicinity of forty degree Celsius may not feel uncomfortable. This is because humidity levels may be too low. In mornings in summers, temperatures are down but we do not feel cooler because of high humidity and do not complain in the afternoon as well because humidity goes down even though temperatures have gone up. It is only when both humidity and temperatures are up that we feel uncomfortable.

There is a natural defense system of our bodies that keeps us cool when temperatures go up. Hypothalamus in brain sends signals to millions of sweat glands and they begin to produce sweat. This sweat, when it evaporates lowers the temperature of our body offsetting the rise in temperature outside. However, it is when relative humidity is high that this sweat is not able to evaporate, and we feel sticky and uncomfortable.