Whether a swamp cooler works depends on the climate in your area. In this article, we’re having a quick glance at all US states and whether swamp coolers work there or not.
Quick answer: Swamp coolers work in almost every US state during the afternoon, because that is the driest time of the day. Using a swamp cooler all day and throughout the year only makes sense in Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming.
Does a swamp cooler work in your state?
I spent some time figuring out in which states swamp coolers make sense according to average humidity values.
If you stick out until the end of this article, you will see why these average humidities are useless to determine swamp cooler effectiveness.
But let’s have a look at the data first. Don’t take the “Does a swamp cooler work in this state”-column too seriously for now.
| State | Average relative humidity | Does a swamp cooler work in this state? |
| Alabama | 68% | no |
| Alaska | 71% | no |
| Arizona | 39% | yes |
| Arkansas | 67% | no |
| California | 69% | no |
| Colorado | 48% | yes |
| Connecticut | 66% | no |
| Delaware | 67% | no |
| Florida | 72% | no |
| Georgia | 68% | no |
| Hawaii | 64% | no |
| Idaho | 55% | yes |
| Illinois | 71% | no |
| Indiana | 71% | no |
| Iowa | 67% | no |
| Kansas | 65% | no |
| Kentucky | 67% | no |
| Louisiana | 74% | no |
| Maine | 72% | no |
| Maryland | 65% | no |
| Massachusetts | 67% | no |
| Michigan | 73% | no |
| Minnesota | 67% | no |
| Mississippi | 73% | no |
| Missouri | 68% | no |
| Montana | 58% | yes |
| Nebraska | 68% | no |
| Nevada | 52% | yes |
| New Hampshire | 69% | no |
| New Jersey | 71% | no |
| New Mexico | 45% | yes |
| New York | 72% | no |
| North Carolina | 68% | no |
| North Dakota | 66% | no |
| Ohio | 69% | no |
| Oklahoma | 64% | no |
| Oregon | 72% | no |
| Pennsylvania | 66% | no |
| Rhode Island | 68% | no |
| South Carolina | 68% | no |
| South Dakota | 68% | no |
| Tennessee | 69% | no |
| Texas | 66% | no |
| Utah | 55% | yes |
| Vermont | 68% | no |
| Virginia | 68% | no |
| Washington | 73% | no |
| West Virginia | 71% | no |
| Wisconsin | 71% | no |
| Wyoming | 53% | yes |
The humidity data in the table is based on this source.
Why you can’t trust the data
The table contains average humidity climate data. If the average humidity in a given state is smaller than 60%, it states that a swamp cooler works, else it doesn’t.
However, you can’t fully trust the table with its climate averages when it comes to using swamp coolers.
Usually, you need a swamp cooler when it is exceptionally hot. So, by definition, average data is not useful.
For example, the average humidity in California is 69% and comparably high. Which is why the table above states that a swamp cooler is ineffective there.
However, the table above includes the average humidity levels over an entire year, including summer and winter, which have vastly different climates. Also, it does not differentiate between morning and afternoon humidity.
Morning and afternoon swamp cooler usage
Mornings tend to be humid (you can tell because of the morning dew), while afternoons and evenings are comparably dry.
Let’s have another look at all US states, but this time let’s check if a swamp cooler works there in the afternoon.
| State | Average relative humidity in the afternoon | Does a swamp cooler work? |
| Alabama | 52% | yes |
| Alaska | 64% | no |
| Arizona | 25% | yes |
| Arkansas | 49% | yes |
| California | 62% | no |
| Colorado | 35% | yes |
| Connecticut | 52% | yes |
| Delaware | 54% | yes |
| Florida | 57% | yes |
| Georgia | 50% | yes |
| Hawaii | 56% | yes |
| Idaho | 41% | yes |
| Illinois | 58% | yes |
| Indiana | 58% | yes |
| Iowa | 56% | yes |
| Kansas | 50% | yes |
| Kentucky | 55% | yes |
| Louisiana | 61% | no |
| Maine | 61% | no |
| Maryland | 52% | yes |
| Massachusetts | 59% | yes |
| Michigan | 61% | no |
| Minnesota | 55% | yes |
| Mississippi | 54% | yes |
| Missouri | 53% | yes |
| Montana | 45% | yes |
| Nebraska | 53% | yes |
| Nevada | 32% | yes |
| New Hampshire | 53% | yes |
| New Jersey | 59% | yes |
| New Mexico | 29% | yes |
| New York | 61% | no |
| North Carolina | 52% | yes |
| North Dakota | 51% | yes |
| Ohio | 57% | yes |
| Oklahoma | 48% | yes |
| Oregon | 59% | yes |
| Pennsylvania | 54% | yes |
| Rhode Island | 57% | yes |
| South Carolina | 49% | yes |
| South Dakota | 53% | yes |
| Tennessee | 53% | yes |
| Texas | 49% | yes |
| Utah | 43% | yes |
| Vermont | 58% | yes |
| Virginia | 52% | yes |
| Washington | 62% | no |
| West Virginia | 59% | yes |
| Wisconsin | 58% | yes |
| Wyoming | 43% | yes |
As you can see in this afternoon-humidity table, a swamp cooler works in almost any US state in the afternoon and early evening heat.
So, getting a swamp cooler for the very hot and dry summer days is worth it almost anywhere.
A typical 24-hour humidity chart looks like this:
As you can see in the sample data above, the humidity reaches almost 80% humidity during the night time. However, during day time, humidity sinks below 20%.
Of course, this is an extreme example. Here, the humidity varies by >60%! Some places never reach humidities below 30%.
But a variation of 40-50% is definitely possible in most places.
And that’s what everybody forgets about. Everybody claims that getting a swamp cooler is not worth it in the more humid states.
Yes, that’s true if you assume that the actual weather sticks to the average values. But that’s not how weather works.
We have sunshine and rain, hot and cold. And it always alternates. Using averages makes no sense when it comes to evaluating whether to use a swamp cooler.
So, even in humid states, you will have hot and dry days. On these days, a swamp cooler is definitely worth getting.
Climate zones within states
Furthermore, there are very different climate zones within states.
For example, in California, there is the bay area, which is humid, and the deserts in the backcountry deserts, which are very dry.
While in the bay area, a swamp cooler does not make sense, in the dry areas it does make sense.
That is the case for almost any state. Even if the tables above say that on average a swamp cooler is not worth getting, oftentimes it can still be worth it, depending on the humidity at your home.
How to measure your home’s humidity
The best way to tell whether a swamp cooler works where you live is to measure your local humidity.
After you know the humidity levels around your house, you can tell whether the local weather around your home deviates from the state-wide average.
You can easily measure humidity using a hygrometer (click here to view it on amazon).
For example, where I live, there is vastly different climate than in the other parts of my state. That’s because my home is in an area with small mountains and a lot of forest.
When I watch weather forecasts, I can immediately tell that the temperature at my home is going to be at least 5°F cooler.
Alternatively: You can also check your city-specific climate online. I like to use weather.com. Enter your city in the search box and view the weather table.
How to interpret humidity readings for swamp cooler effectivity
Once you have the humidity readings of your hygrometer (or the weather website), you can judge whether a swamp cooler is worth getting.
Here’s the golden swamp cooler rule:
“A swamp cooler is worth running if the humidity reaches 50% or lower over the course of a day”
So, even if mornings are very humid in your area (as they are in most places), a swamp cooler is still worth getting if the humidity decreases during the hot hours of the day.