can relative humidity exceed 100

Can relative humidity exceed 100? Measuring the relative humidity levels is important to make your house more comfortable to live in.

Experts believe that you should maintain relative humidity between 30% and 50% for optimal comfort and health.

But, it seems that the more pressing question is, can humidity exceed 100 percent? And what happens if it really does?  

While it may not seem very intuitive, the relative humidity levels can exceed 100% in some cases. 

What is Relative Humidity?

what is relative humidity

Relative humidity is a meteorological term used to describe the amount of humidity (how heavy or how dense the air is) as a number.

As a mathematical expression, it provides the ratio of water vapor present to the greatest amount possible the air can hold which is saturation and 100%.

Once saturation reaches 100%, the air cannot support any more vapor.

Its density is such that there is no space available for more water vapor molecules and so no more is absorbed.

Fact: "Relative humidity" refers to the percentage of humidity, expressed as a range from 0% to 100%. 

Importance of Monitoring Relative Humidity (RH)

Preventing relative humidity from reaching unsafe levels is crucial. 

RH in Storage Spaces

rh in storage spaces

If the relative humidity (RH) in the storage space stays too high for too long, moisture will accumulate on the surface of different products, which can spoil them.   

RH in Pharmaceuticals

Certain medications and other items are extremely vulnerable to even trace amounts of moisture, making humidity an additional major issue.

Therefore, things like pharmaceutical tablets and dry powders require careful storage at precisely calibrated humidity and temperature levels

RH in Automation Systems

Last but not least, relative humidity is also a significant influence in building automation systems like air conditioning.

The capacity to monitor and adjust relative humidity (RH) is important for a number of reasons, including:

  • Optimizing the efficiency of HVAC systems
  • Ensuring that occupants are comfortable no matter the weather outside

This implies that it is essential to keep track of humidity levels in different settings. Maintaining the right levels in your home is also important.

But, besides knowing what is normal, it is also essential to know how high the RH can go.

Fact: As perspiration evaporates at a slower pace when the humidity is high, perspiring is less effective at cooling the body. 

Can Relative Humidity Exceed 100?   

can relative humidity exceed 100%

Yes, humidity levels can exceed 100% although it may seem counterintuitive. When humidity levels are over 100, the air is described as supersaturated.

It simply means it contains more of a substance than it can absorb, the substance, of course, being water vapor. 

Humidity, temperature, and pressure are interrelated in so many ways.

The warmer the air, the more water vapor there is in it and the lower the pressure is. Therefore, supersaturation tends to happen more in hot tropical climates.

It is mainly because the higher temperatures provide more energy for the water molecules as they change from a liquid to a gas during the process of evaporation. 

Is 110% Humidity Possible?

Okay, so can humidity be over 100? Yes. It can go up to 110%.

This means there is 10% more water vapor available in the air than can be converted to vapor in a given space in the air.

Since the molecules are not vaporized, they can only stay as they are, in a liquid state.

possibility of 110% humidity

They collect wherever the temperature is cooler, such as on windows where they can fully condense and coalesce into water droplets.

Other examples of condensation are:

  • Water droplets on the glass containing a cold drink
  • Fogged-up glasses or bathroom mirror
  • The air we breathe out in winter
  • Contrails and clouds
  • Dew on the grass

The dew point is the temperature air needs for the relative humidity to be at 100%.

At the temperature, dew is formed and the water vapor condenses, typically on grass but on all cold surfaces.

And in the air as fog, the water vapor condenses at the same rate as the liquid water evaporating. 

The two processes are equilibrium and the dew point can therefore be used as a measurement.  

Is There Such a Thing as 200% Humidity?

Yes. Although this level of saturation doesn’t occur naturally.

Present concerns are over how, due to climate change, increased temperatures will create levels of humidity that the human body and mankind’s existence are not adapted to.

possibility of 200% humidity

Over the last 40 years, levels of heat stress have doubled and more is expected.

We are likely to get more used to considering the heat index before leaving the house.

The heat index is a measure used in weather reporting to describe how the air temperature feels on the skin and has relative humidity factored in. 

What is the Highest Relative Humidity?

In laboratories, scientists have been investigating humidity levels of up to 800% in order to understand the impact of climate change. 

It is a humidity level that is unlikely to support life as we know it, at least on Earth.

In the natural world, the highest levels of humidity recorded have been at coastal locations along the equator. 

One of the highest was in Saudi Arabia with a dew point of 950 F.

The dew point is the temperature at which air is saturated with water vapor. 

The Concept of Wet-Bulb Temperature

Another term scientists are using more when researching global relative humidity is ‘wet-bulb temperature’.

The wet-bulb test compares the difference in temperature when the thermometer bulb is dry to when a cloth covers it at room temperature wet.

concept of dry and wet bulb hygrometer

 It is a way to measure evaporation. In low-humidity conditions, the wet-bulb temperature will be below the dry-bulb temperature.

The process of evaporation, which results in a decrease in temperature, is responsible for this.

Globally, the instances of wet-bulb temperatures reaching 950F are increasing and climate models predict that the Persian Gulf, South Asia, the Red Sea, Eastern China, Southwest Asia and Brazil are all vulnerable.

Fact: Humidity is typically low in deserts and high in tropical places.

Will it Rain if Relative Humidity is 100%?

fog due to high relative humidity

No, not always.

When a certain location reaches a relative humidity of 100%, it simply means the dewpoint temperature and the actual air temperature are the same.

 Also, it implies the maximum amount of water vapor the air could hold, has been reached.

The air is saturated. The water molecules the air cannot contain collect and stick together as droplets to eventually form fog at ground level, or clouds.

This process is called ‘collision-coalescence.’

To form rain, the air must rise to an altitude where it will lose its heat in colder air. 

There, the water vapor condenses into suspended droplets of liquid water or ice. Once they have sufficient size and mass they fall as rain. 

An Important Thing to Consider

cloud thunderstorm

Areas of high humidity do experience thunderstorms sometimes with predictable regularity.

These regions have the optimal warm and wet conditions needed for superstorms.

It happens when massive amounts of warm air rapidly rise through the atmosphere to cool at very high altitudes forming enormous anvil-shaped clouds.   

What Happens When Relative Humidity is High?

High temperatures are stressful for the body. Internally regulating our body temperature uses a lot of energy although this is more noticeable in the cold when we shiver.

Effects on Body

In humid conditions, the body’s primary mechanism for cooling, sweating, is disabled.

Normally, humans sweat to cool down as the perspiration produced evaporates away from our body.

You might notice the cooling effect after stepping out of the hot shower. This cannot happen when the air immediately around us is already moisture saturated.

We tend to function better when humidity is low and temperatures are high. 

Effects on Property

molds due to high relative humidty

Apart from making us feel lethargic and uncomfortable, high humidity affects our environment. 

Living where relative humidity can reach 70% or more creates all kinds of problems.

Mold flourishes and corrosion accelerates, paintwork cracks and the wood shrinks. All play havoc around the home.

Fact: It is possible to measure humidity with hygrometers, often used by meteorologists to determine the relative humidity of the air. 


Can relative humidity exceed 100%? Yes, it is possible; in fact, relative humidity can go much higher than that, but it is quite rare in the real-world.

The thing is that you are likely to develop all sorts of problems at a humidity level much lower than 100%.

In fact, you need to keep it around 40%, and that is why you have to take advantage of dehumidifiers whenever needed.