Explainer: Relative Humidity  

Evaporative cooling, the Quilo manual states, is ideal for dry regions with a relative humidity of less than 45%. Humidity is a well-known term – it’s that hot, sticky feeling on a sweltering summer day. But what is the definition of “relative humidity”? And why do we use percentages as a way of measuring it? After all, temperature is measured in degrees – why wouldn’t humidity be measured in degrees too?  

What is Relative Humidity? 

Relative Humidity (RH) is a ratio. It measures how much water vapor is present in the air on a scale where 100% is the maximum water vapor that a cubic meter of air could carry. For example, a relative humidity level of 50% means that the air is 50% saturated with water vapor.  

So far so good? Now let’s add another component into the Relative Humidity calculation. Warmer air can actually contain more water vapor than cooler air. Therefore, a cubic meter of air with a temperature of 70°F would require more water vapor to reach the 50% RH mark than the same amount of air at a lower temperature of 40°F. But interestingly, for humidity to culminate in rain, the relative humidity must reach 100% in the stratosphere where the clouds accumulate. If the air is fully saturated with water vapor closer to the ground, then you get those desperately muggy days when you gaze longingly at the sky, hoping for a break in the heavy heat. 

Is it hot outside? Well, it’s all relative… 

What makes those hot, humid days so unbearable isn’t only the humidity in the air, but also due to the biology of our bodies. We, humans, regulate our temperature through sweating and evaporation. When our bodies are too hot, we produce sweat. As this moisture evaporates into the air, heat energy leaves our bodies, leaving us feeling cooler. (Read here for a more detailed explanation). But when the weather is extremely humid, and the air is already saturated with water vapor, the sweat emitted by our bodies is unable to evaporate into the already saturated air. So, we are left feeling like a cold shower is our only respite!  

In fact, there are real consequences to humidity and how it makes us feel. Take two days with the identical temperature: On one day, the air temperature is 75°F and the relative humidity is 0%. Yet, against our bodies, the air temperature will feel like refreshing 69°F. On the second day, the air temperature is that same 75°F but the relative humidity is 100%, and we will perceive that it’s a stifling 80°F! 

Not too low, nor too high…but just right 

If you had some supernatural powers to create a world with the perfect Relative Humidity, according to the specialists in white coats who have studied these things, the good range is between 30%-70% while the ideal niche is between 50%-60%. When the RH is within these parameters, you get neither the discomfort of excessive moisture nor the irritation from intense dryness.  

For those of us without supernatural powers, if you do want to achieve that perfect humidity in your home, Quilo is here to help. If your climate’s RH is below 30%, then the Quilo 3in1 evaporative air cooler can add hydrating water vapor to your arid atmosphere. If your locale is excessively hot and humid, the Quilo portable air conditioner not only cools but also dehumidifies its environment.  

Next time you hear the meteorologist talking about relative humidity, you can nod knowingly. Now, what exactly is the dew point? 

Quilo Portable Air Conditioner

Cools off humid or very hot, dry enviroments. Can be moved from room to room. Also functions as a dehumidifier.
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About the Author
With a Master degree in Communication, Dena believes that communication can cure society of all its ills. Based in Pittsburgh, she oversees all these written words, digital content and consumer engagement–and when not ensuring world peace through her work for Quilo, can be found out-and-about with her four daughters.

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