Nothing compares to the Iowa State Fair, at least most state fairs don't (as a Minnesotan I'd say the Minnesota State Fair is comparable). However, I am not here to talk about which state fair is best, I am here to discuss the long history of weather during the Iowa State Fair.
Before I get into it, big thanks to the National Weather Service in Des Moines (specifically Craig Cogil) for providing the weather data for this article.
History of the Iowa State Fair
Before we get into the weather side of things, let's talk about how the fair got to the point it is at now.
The first ever state fair was held in Fairfield, Iowa back on October 25-27, 1854. It then bounced around to many different locations through a majority of the mid to late 1800s, including locally in eastern Iowa in Iowa City (1860 & 1861), Dubuque (1862 & 1863), and Cedar Rapids (1871-1873, 1876-1878). It moved to Des Moines in 1879, and after finally getting approval for a permanent fairgrounds in 1886, it's been at the same location ever since.
There have been 6 years that the fair has not been held, and those years are 1898, 1942-1945, and 2020. Below are the reasons for each fair not being held.
1898: The world's fair was taking place nearby in Omaha, along with the ongoing Spanish-American War.
1942-1945: The United States was involved in World War II, and the campgrounds were used as a supply depot for the military.
2020: The COVID-19 pandemic shutdown the fair, but a virtual fair was held in its place on August 13-23.
What's Typical Weather for the Iowa State Fair?
As you may expect, mid August is one of the warmer times of the year. However, the fair wasn't always held in August. Prior to the 1940s, it was mostly held in September or late August. Because of that, the 30 year average of the first 30 years of recorded data in Des Moines vs the latest 30 year average are quite different.
*As a note, weather data for the other cities prior to being held in Des Moines are not readily available. Also, as another footnote, from 1879 to 1939, the observations for Des Moines were recorded at a location close to the US Courthouse in downtown Des Moines. From 1940 onward, observations are recorded at the Des Moines International Airport. While temperatures won't vary much between these two locations, rainfall could be different in very short spaces. Keep that in mind as you read the rest of this data.
Comparing the first 30 year time frame (when it was first held in Des Moines) to the latest 30 year time frame, moving the fair back a month makes quite the difference. The normal high, low, and rainfall is all higher in the latest 30 year time frame than the first 30 year time frame. August is usually not only warmer than September, but wetter as well (more heat leads to more moisture), so this data makes sense.
Above is a look by decade at the normal highs, lows, and rainfall for the Iowa State Fair. Notice the gradual warm up through the 1920s. The state fair was held in September through the 1930s, but has shifted back to August in the 1940s and has been there ever since.
Bring on the Heat
Unfortunately, not every year is confined to normal temperatures. Mother Nature can bring the heat, and in some years, she REALLY brought the heat.
Taking the average temperature through the entire fair, including the day and night conditions, 1983 was far and away the warmest state fair, averaging 84.4 degrees. The next closest was 1937 at 80.9 degrees. Remember, in the 1930s, the fair was still held in September, so those dust bowl years are not up there for that reason. Had it been held in August, these records would hold many of the 1930s.
Moving on, rounding out the top 5 is 1975 with an average of 80.4 degrees, 1995 with an average of 80.0 degrees, and 2007 with an average of 79.6 degrees.
There have been 6 days that the Iowa State fair has reached a daily high of 100 degrees or higher, and they all came back in 1983. No other year has had a single high temperature greater than 100 degrees, which is absurd since the data goes back to 1880.The average daily high for that year 96.8 degrees! 1988 was one of the hotter years on record, but the records set during August were just before the state fair. 3 other days came close at 99 degrees. Those days were August 23rd, 1975, August 27th, 1955, and August 24th, 1947.
Not Every Year Was a Sauna
The state fair has had its fair share of cooler years too, but notice that all of them are prior to the 1940s. Again, this is because of the later time frame of the state fair being held in September. The coolest year for a fair held completely in August was 2004, with an average temperature of 65.3 degrees.
Similar to the coolest years, the lowest daytime highs were predominantly in September, however, 2 of the 5 coolest were in the month of August. The record for the coolest night ever was September 1st, 1949 at 38 degrees, the only ever night in Iowa State Fair history to dip below 40 degrees.
The Umbrella Worked Overtime Some Years
If you were at the fair in 1977, chances are you got wet, as a whopping 8.46 inches of rain fell that year. A majority of that came on two days: August 26 at 4.18 inches (the highest ever rainfall in one day in fair history), and August 27 at 2.29 inches (the 9th highest ever rainfall). The next closest was 6.22 inches of rainfall in 1993.
On the contrary, we've had 3 years of no rainfall, including most recently 2021, along with 1939 and 1893. 5 years have seen purely a trace, including as recently as 1986, and 7 years saw just 0.01 inches of rainfall.
This Year's Forecast
Today was comfortable to kick off the fair, and this weekend is no different, with highs cooler than normal and dew points in the 50s. While next week brings a few storm chances and a rise of highs back into the 80s, this year's edition will be nowhere close to the hottest or wettest on record.
For those of you heading out to the fairgrounds, enjoy your time along with the nice weather!
