Extensive research that we completed in the middle 1990s in regards to the Sunspot Cycle suggested that the period from 1996 to 2008 “should” have featured several very hot summers for the Nation, and indeed that forecast verified as it was during that period that the United States recorded eight of its 25 hottest summers on record (going back to 1895). Ironically, at no time during that period did Des Moines, IA set a record high during the meteorological summer (June 1 through August 31). In fact, Des Moines did not set any record highs in the summer for the last two complete DECADES. One has to go back to 1988 to find the last time that Des Moines set a record high in any summer month, and one has to go back to 1955 to find the last time that Des Moines set a record high in July.

Some may point out that it is not easy to set record highs. Valid point…but consider the following:

a) In the same time (1990 to 2010) that Des Moines set no record highs in the summer, Des Moines set or tied no less than 26 record highs in the winter, 20 in the spring, and 18 in the fall. It HAS been easy to set record highs in Des Moines…just not in the summer.

b) Des Moines currently has in its record books at least one summertime record high from EVERY decade going back to 1900…except for the last two decades.

Not only has it been hard to set record highs at Des Moines in the summer, it has become quite difficult to simply get hot days at Des Moines. After averaging a little more than two days each year with 100 degree high temperatures from 1900 to 1989 (an average that was maintained during the two-decade period from 1970 to 1989), Des Moines averaged just ONE such day every THREE YEARS during the two-decade period of 1990 to 2009. Des Moines averaged only about 7.5 days with highs at 93 degrees or higher from 1990 to 2009, but for the 90 years previous to that the average per year was nearly double at 13.9 days per year.

How does one explain this incredible weather irregularity?

If it seems like it has been a long time since the Midwest has seen a major, “headline-making” summer drought, you are right. While there have been various growing seasons with “dry spells” embedded within them (1991, 1995, 2002, and 2003 quickly come to mind as years in which national corn and/or soybean yields were down from what would be considered “normal” levels), one really has to go back to 1988 to find the last time that national corn and soybean crops were a “disaster” in the same year due to a lack of rain in the summer. Going 22 years without a drought is unprecedented in my opinion (at least for as far back as we have good weather data, which is 1895). Not only have we had a lack of drought since 1988, that same 22-year period has featured some very wet summers, with rainfall in the summers of 1993, 2008 and 2010 being some of the highest ever recorded for very large parts of the Corn Belt.

How does one explain this incredible weather irregularity?

One possible explanation for both of these “irregularities” is that we have changed our summer climate (at least to some degree) due to

• increased acreage devoted to corn and soybeans in the Midwest;
• plant populations of corn and soybean acreage increasing;
• corn and soybean hybrids becoming so drought resistant; and
• minimum- and no-till farming becoming so popluar.

Though our research on this subject has been done independently, it is a subject that has been researched by others in recent years as well (such as Richard Raddatz at the University of Winnipeg and David Changnon of Northern Illinois University).

If you would like further details into this study, please feel free to contact us at craigs@weather.net