Humidity and temperature are correlated. Our perception of temperature is affected by humidity levels. We are talking about the humidity and temperature relationship.
Questions like “At what temperature does humidity feel colder?” or “Do we feel warmer when humidity levels are lower?” steer from this relationship. This is the classic moist heat vs dry heat situation.
In short, we feel that humid air is hotter than it really is. Reversely, we also feel that dry air is colder than it actually is.
This is true if we talk about the indoor temperature (in the house) as well as the outdoor temperature.
In order to fully understand how does humidity affect the temperature in a house, we only need to look at one chart. This is the ‘Temperature And Humidity Relationship Chart’:
This chart tells us everything we need to know about how humidity affects our perception of temperature.
Example: Let’s say that we have a 75°F temperature in a house. That means that if we check the thermometer, it will always read ’75°F’. However, we won’t always feel the indoor air at 75°F. Humidity plays a big role in how we perceive air temperature. Namely, we will perceive 75°F temperature as:
- 70°F at 10% humidity levels.
- 72°F at 20% humidity levels.
- 73°F at 30% humidity levels.
- 74°F at 40% humidity levels.
- 75°F at 50% humidity levels.
- 76°F at 60% humidity levels.
- 77°F at 70% humidity levels.
- 78°F at 80% humidity levels.
- 79°F at 90% humidity levels.
- 80°F at 100% humidity levels.
As we can see from the temperature and humidity relationship chart, 75°F can feel like 70°F at very low humidity levels (10% moisture levels) or 80°F at very high humidity levels (100% moisture levels). This is a full 10°F range; meaning that humidity levels have a substantial effect on the temperature levels we feel.
Let’s first look at why our perception of how hot/cold air depends on humidity. After that, we will look in-depth at how humidity affects the temperature based on the Temperature And Humidity Relationship Chart:
Why Does Humidity Affect The Temperature? (Perception-Bias)
It’s quite unusual how we can’t really percept actual temperature; we have a built-in bias as humans. Why exactly is this?
The key factor in humidity-temperature effects is explained by water evaporation from our skin (perspiration). Namely, our bodies cool themselves by water evaporation from our skin. When the heat is really intense, we start to sweat in order to cool ourselves. Sweating just adds to the amount of water that can be evaporated from our skin.
Perspiration is an endothermic process; it cools our bodies. This is the very process that determines how we perceive temperature.
This is because perspiration depends on humidity levels.
When the air humidity is very high, the perspiration process is impeded; it will be harder for water to be evaporated from our skin into the air since the air is already quite moist (full of water). Hence our ability to cool will be obstructed and we will feel that the temperature is hotter than it actually is.
When the air humidity is very low, the perspiration process can speed up. That’s because there is less moisture in the air and the surrounding air will more readily accept water that is being evaporated from our skin. This means that our ability to cool will be improved and with more cooling, we will feel like the temperature is colder than it actually is.
Based on the understanding of how perspiration and humidity levels are connected (inverse relationship; more humidity equals less perspiration), we can figure out why dry heat feels less hot than wet heat.
What is more, we can quantify exactly how hotter or colder a humid or dry climate is, respectively. We can summarize these perceived temperatures in a neat chart:
Temperature And Humidity Relationship Chart
This temperature humidity chart tells us how hot the air actually feels at a certain temperature and humidity points:
The red arrows show you at what humidity the perceived temperature is the same as the actual temperature. These points are:
- At 70°F and 60% humidity, we actually feel the temperature is indeed 70°F.
- At 75°F and 50% humidity, we actually feel the temperature is indeed 75°F.
- At 80°F and 45% humidity, we actually feel the temperature is indeed 80°F.
- At 85°F and 35% humidity, we actually feel the temperature is indeed 85°F.
- At 90°F and 30% humidity, we actually feel the temperature is indeed 90°F.
- At 95°F and 27% humidity, we actually feel the temperature is indeed 95°F.
- At 100°F and 22% humidity, we actually feel the temperature is indeed 100°F.
- At 105°F and 20% humidity, we actually feel the temperature is indeed 105°F.
- At 110°F and 18% humidity, we actually feel the temperature is indeed 110°F.
- At 115°F and 15% humidity, we actually feel the temperature is indeed 115°F.
If you want to know how humidity affects the temperature in a house, the first three temperatures (70°F, 75°F, 80°F) are the most relevant since the indoor temperature is usually within this range.
As you can see, by decreasing indoor humidity levels below 45% in the summer, we will effectively feel cooler in the summer. To feel cooler, it pays off to run an air conditioner and dehumidifier at the same time, for example.
Other temperatures are relevant for how humidity affects the temperature outdoors.
Example: In 100°F outdoor heat, we will only feel its 100°F at 22% humidity. If the humidity levels would be 80%, it will feel like 157°F (that’s why Florida is close to hell temperatures in the summer).
We hope that this helps in understanding how humidity can affect the temperature. If you have some questions about this, you can use comments below and we’ll try to find an answer for you.