Changing Rainfall Patterns

Statewide annual total precipitation has increased by nearly 6 inches between 1895 and 2019, an approximate 15% increase, as shown in the figure below. According to the National Center of Environmental Information (NCEI), these numbers significantly exceed the national average precipitation increase of 4% (4-5).  Long-term increases in local precipitation can degrade water quality, strain drainage systems, and disrupt ecosystems. Climate change projections indicate rainfall amounts will continue to increase in Illinois.  

Figure 3: Precipitation Trends from 1895-2021 for Illinois (NOAA/NCEI, 2021)

We are also experiencing more intense rain events in Illinois (Frankson et al.). Higher temperatures allow the air to hold more water, which in turn causes more intense rainfall.  According to the report,  “Building Resiliency to Climate Change: A Call to Action,” by the Illinois State Water Survey, the state of Illinois has a long history of infrastructure and property losses due to flooding (13). All 102 Illinois counties have experienced flooding severe enough to warrant a Presidential Disaster Declaration. Climate change is expected to make this trend worse. Between 2001 and 2013, Illinois had a flood-related disaster declaration nearly every year. Increased rainfall intensity can cause flooding along rivers and inside homes. Flooding ruins crops, causes soil erosion, and pollutes our water. Without climate action, flooding events are likely to increase, bringing more danger and damage to Illinois communities and natural resources.