Do Evaporative (aka Swamp) Coolers Work In My Area? Find Out With Our Evaporative Cooler Humidity Chart

Do you want to know if an evaporative cooler will work in your area? This is an incredibly common question we receive, so in this post, we are going to answer the question in some detail.

How does an Evaporative Cooler Work?

First of all, it’s important to understand how an evaporative cooler, also referred to as a swamp cooler works. As their name suggests, they work on the principle of evaporation.

You have probably experienced evaporation yourself. It’s the cold feeling you experience immediately after stepping out of a pool into the open air. This almost instant cooling is the result of the dry air passing over the water which absorbs some of the water molecules.

The exact physics behind this phenomenon is quite complex, but the absorption results as the temperature and vapor pressure of the water try to equalize with the air.

In simple terms, this process involves some of the water molecules turning into gas molecules and heat is transferred from the higher air temperature to the lower water temperature. This means that the air surrounding it is cooled.

Evaporative coolers available for purchase utilize this exact principle. Inside of most units, you will find a fan and a water-soaked pad. The fan functions to draw in the hot, dry air from outside and pass it through the water containing pad. This results in heat being absorbed from the air and re-circulated back into the room as cool and gentle breeze.

Swamp Cooler vs AC

The majority of people living on the east coast of the United States likely aren’t familiar with swamp coolers. This is due to the fact that an evaporative cooler will work much better the farther you go west.

So, what is the major difference between a swamp cooler vs ac? As the majority of people know an ac works best when windows remain closed in a home or car so that the cold air is trapped and isn’t able to escape to the outside environment. 

A swamp cooler works in an open-system, opposed to the ac’s closed-system. Unlike an ac, a swamp cooler’s air flow needs to be regulated to ensure you are maximizing it capability.

Similar to ac units, however, swamp coolers can also create a hotbed when it comes to fungal populations. According to a study completed in 2018, many Ascomycota detected in evaporative cooler “environments were several species capable of producing major fungal allergens. 

As with any potential airborne issues that can be found present in our environments, you need to be aware of when an appliance needs to be cleaned and disinfected to keep the spread of any potential harmful diseases or allergens at bay. 

Will an Evaporative Cooler Work in Your Area? 

Since evaporative coolers and swamp coolers rely on the principle of evaporation, they work better in certain areas of the country.

Typically they work best in dry, warm regions. The main reason for this is due to the fact that swamp coolers rely on dry conditions for the cooling process to occur. Since evaporation will also result in an increase in air moisture levels, it can also be good or bad depending on your location.

Evaporative Cooler Chart 

If you want to get a better idea as to whether you live in an area or state that is suitable for a swamp cooler, then this evaporative cooler chart will provide you with a good idea. This is largely based on humidity levels, the lower it is, the better the evaporative cooler will work.

evaporative cooler humidity chart

The map shows the humidity levels across the United States and therefore provides a good indication of where swamp coolers will operate most effectively. As you can see, the pattern is that the further west you are located, the more suitable an evaporative cooler is going to be.

  • Zone A: Ideal for Evaporative Cooler Use
  • Zone B: Less Ideal for swamp cooler use, but still effective to some degree
  • Zone C: Evaporative coolers are not effective in these regions (air conditioners are preferred)

Evaporative Cooler Humidity Chart 

Whether an evaporative cooler is suitable for your situation is based on two factors in your local environment: average air temperatures throughout the year and relative humidity levels. An alteration in either can result in performance changes and impact how much of a decrease in temperature an evaporative cooler can achieve.

Therefore, in order to determine if your evaporative cooler will work at its optimum and to see what type of temperature drop you can expect, you can use an evaporative cooler humidity chart. The chart takes into account the following principles:

Air Temperature: The air temperature alone won’t provide enough information to know whether a swamp cooler will work effectively. Standard thermometers provide what is often referred to as a “dry bulb temperature”, this is a reading without any other influences accounted for e.g. humidity or moisture content in the air.

The wet-bulb temperature does take into account humidity and is often determined by placing the thermometer in wet material. As water evaporates from the thermometer, this reduces the temperature around the thermometer, resulting in a reading that better represents the influence of humidity.

The dry bulb temperature and wet bulb temperature can then be compared. If the latter is a lower temperature, than the dry that means that humidity in the air is low and evaporation is occurring at an effective rate.

Relative Humidity: Humidity simply measures the amount of moisture in the surrounding air. Relative humidity refers to the total amount of moisture that can be held in the air at a certain temperature. For example, a reading of 100% relative humidity means that the air is as saturated with moisture as possible, making evaporation unfeasible. This is why swamp coolers are not at all viable in very humid locations such as south-east.

evaporative cooler humidity chart

How to Use the Evaporative Cooler Humidity Chart 

Please bear in mind, that the evaporative cooler humidity chart does assume you are using the correct size evaporative cooler for the area you intend to cool.

As you can see the chart is read using your air temperature (on the left) and your relative humidity (on the top). Once you have these measurements you simply follow them on the chart until they intercept each other and that is your score.

For example, if your average air temperature was 85 degrees and your relative humidity was 35%, your swamp cooler would be able to achieve a temperature of 71 degrees. So, in total that’s a temperature drop of 14 degrees.

As you can see, the numbers highlighted in blue represent the optimum conditions for evaporative coolers. So if you end up with a score that is highlighted blue that is ideal, and if not the closer the better.

Using this evaporative cooler humidity chart can provide you with a good idea as to whether an evaporative cooler is right for you and space you intend on cooling.

Final Thoughts 

Evaporative coolers or swamp coolers are an effective way of cooling and achieving temperature reduction in certain locations of the United States. Many people prefer them over air conditioners, as they have significantly lower running costs.

In order to determine if a swamp cooler is suitable for your location, you can use the evaporative cooler map above. If the answer is yes, you can then determine what temperature drop you may expect using the evaporative cooler humidity chart.

Bear in mind, that you will need to select a swamp cooler that is designed to cool the size of the area you have in mind.

If you do discover an evaporative cooler isn’t suitable for your particular circumstances, don’t be too disappointed as there are many other cooling options available e.g. a sliding window air conditioner, a heat pump or perhaps a small air conditioner unit.