Illinois State Water Survey - University of Illinois at Urbana-Champaign

State Climatologist Office for Illinois

Climate Change in Illinois

Dr. Jim Angel, State Climatologist

Global warming, or more precisely global climate change, has become a major issue in the last few decades. Climate change in Illinois, the nation, and the world has had and will continue to have direct and indirect impacts on Illinois.

We know the climate in Illinois has changed in the past due to natural forces such as changes in the amount of solar radiation, ocean circulation, and volcanoes. Humans can impact climate on a local, regional, and global scale, through increases in greenhouse gasses, changing aerosols (small particles in the air such as dust or sulfates from coal burning), and land use changes (change from prairie to agriculture to cities). Therefore, climate change is the result of complex interactions between natural and human-induced forces and remains a challenge for understanding future climate change.

The Water Survey is dedicated to monitoring and understanding climate change in Illinois. This site provides some insights on climate change in Illinois and how it relates to the U.S. and the world. A more extensive discussion of the past climate and possible scenarios of the future climate of Illinois can be found on the Illinois Water Supply Planning web page.

National Climate Assessment: Midwest Region

The 2014 National Climate Assessment reviewed climate trends across the Midwest, including Illinois, in this chapter report. Extreme heat, heavy downpours, and flooding will affect infrastructure, health, agriculture, forestry, transportation, air and water quality, and more. Climate change will also exacerbate a range of risks to the Great Lakes. Explore how climate change is affecting the Midwest. The report also has chapters by sectors such as water, agriculture, transportation, forestry, and human health. In addition, there are response strategies presented mitigate or adapt to the current and expected trends. The full report can be found at the National Climate Assessment website. The next National Climate Assessment is currently underway and is expected to be released by 2018-19.


Here are the annual temperature and precipitation trends for Illinois. A more detailed analysis, including tentative conclusions of the 1800s, can be found here


Illinois temperature trend


Illinois precipitation trend

Here are two great interactive resources for plotting time series of temperature and precipitation for Illinois or elsewhere

United States

The National Climatic Data Center tracks US temperature and precipitation trends at NCEI Climate at a Glance. Here are the US trends in annual temperature and precipitation through 2015.


Calculating the Earth's temperature is very challenging. Changes in sites, exposure, instruments, procedures, and observers can introduce errors and biases into the data. Observations before 1900 were more sparse and were concentrated in the land areas of the northern hemisphere. However, extensive research has gone into accounting for these issues.

While no data set is perfect, several groups applying different techniques have reached similar conclusions. Furthermore, other kinds of observations support the evidence of warming. These include the observed reduction of glaciers in every continent, reductions in snow cover, shorter ice season on many lakes and rivers, and changes in the oceans.

Groups who have calculated global temperatures include NASA's Goddard Institute for Space Studies (GIS), the U.S. National Climatic Data Center.

These data are updated frequently at the NCEI global temperature page.

Illinois State Water Survey Resources

Illinois State Water Survey

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