Historical Weather Observations at the WCROC

March 23, 2018

Weather affects our daily lives, from planning our day-to-day activities to planting our fields or gardens to deciding how to dress.  We rely on the weather forecasts to make our plans, but often take for granted the process of collecting this important information.    

Weather data at the West Central Research and Outreach Center (WCROC), Morris, is one of oldest weather data sets in the Western Plains.  Our weather station was established on April 15, 1885 by the Army Signal Corps.  The station was located near 400 East 4th Street, and readings were made by D. T. Wheaton.  On October 4, 1919, the station instruments were moved to the West Central Ag Experiment Station, which was located on the UMM campus.  The weather instruments were later moved to the experimental plot area at the WCROC on September 1, 1973, where they currently reside.  

Average Yearly Temperature

Figure 1: Average Yearly Temperature at the WCROC

Along with the longevity of our weather records, we’ve maintained them at a completion rate of 96%.  This is one of the highest competition rates of weather records in North America.  When considering how this was accomplished, one cannot help to think about the dedication of the staff collecting the data over the last 133 years.  Much of this data is collected manually.  Rain and snow fall, frost depth, and the evaporation pan is still taken manually.  It was not until 1983 that we had automated temperature recording equipment.  To put this in perspective, since April 15, 1885, someone has walked out or traveled to the weather station every day and collected data on temperature, rain and snow fall and other measurements 96% of the time.  The data was faithfully collected in blizzards, freezing temperatures and during other hardships, such as the Spanish flu epidemic that occurred in 1918. 

WCROC staff write a monthly report of the weather data collected, which is published in the Stevens County Times newspaper.  We usually do not talk of trends and look at the weather from a historical perspective in the monthly report.  However, our annual weather report allows us to look closer at how the weather is changing here in Morris, and how it may affect crop development and yields.  (View our annual weather reports

In the last 133 years, our mean annual temperature is 42.5 degrees.  The lowest recorded mean annual temperature was 38o F recorded in 1917.  The highest annual temperature was 47.2 o F recorded in 1931.  Figure 1 illustrates the average yearly temperature by year at WCROC.

In the last three years, we have had above average temperatures followed by two years of below average with typical variability.  

Record High Temperatures

Figure 2: Record High Temperatures at the WCROC

One noticeable event is the distribution of record high temperatures.  Record temperatures set during the growing season can be detrimental to crop production, whereas record temperatures that occur in the winter months are often appreciated.  Figure 2 illustrates the distribution of record temperatures for two 3-month periods. The top squares represent the year a record temperature was set for June, July and August.  We see quite a few records set in the 1930’s and 8 were set in 1988 which was a hot drought year.  However, after 1988 we see only 4 new record temperatures from this time.  

The bottom triangles represent record temperatures set in January, February and March.  Since 1988, we have set numerous record temperatures for this 3 month period.  We often write about record temperature in the winter but not in the summer.  This may reflect warmer winter months.

We are also seeing less days over 90o F.  Figure 3 shows the historic distribution of days over 90o F. The upper limit of growing degree days is 86oF; when temperatures are over 90°, crops are stressed.  It would appear we are having fewer days over 90o F in the last twenty years.  However, that is not to say we could not get a repeat of a hot drought year like 1988.  

Days over 90

Figure 3: Days over 90

On average, we have 2,524 growing degree days from April through September.  In the past twenty years, we have not seen much variability compared to the time from 1900 to 1940. 

Another interesting trend we see is reduced evaporation pan measurements.  Data is collected by measuring the evaporation occurring weekly in a round 48 inch pan.  Data for this measurement goes back to 1971.  There has been a considerable change in the trend over the past years.  What we have seen is that we have almost 1/2 the evaporation we had in the early 1970s.  This trend has been noted worldwide and the cause is still debated.   

There are several ways how this data can be applied to agriculture.  It was most likely easier to put up dry hay in the 1970s vs the last ten years.  Diseases that are favored by a wet canopy such as white mold in soybeans have better conditions to live in.  This may be important for many small grain diseases also.  However, this data may reflect less water loss to crops or the potential of reduced moisture stress in recent years.  Water is often one of the most important limiting factors in non-irrigated crop production.  More discussion and research is needed to understand the impact of this observation.

Frost Dates after Sept 1

Figure 4: Frost Dates after Sept 1

Finally, let’s take a look at killing frost (<28o F) dates.  Figure 4 displays this data.  Since 2000, we have had three killing frosts in September, but none were before September 20.  The average frost date from 1886 is 36.6 days after September 1.  If we look at the last twenty years, the average frost date is 42 days after September 1.  Prior to 1937, there was approximately 1 in 10 chance of frost before September 20. 

In conclusion, the weather records at WCROC show changing weather patterns.  However, this is expected as we look back at in our weather history.  While our extensive weather records are just one of many important weather observation sites in the country, the data can be useful to area farmers, homeowners, and weather observers.  For more weather related data taken at the WCROC, visit https://wcroc.cfans.umn.edu/weather.