In 2026, Illinois has set a new annual record number of tornadoes (by July), set a new state hailstone record, and withstood flash floods, derechos, and seemingly everything in between — and it’s only September! Let’s review some of the severe weather in Illinois this year so far.
Record Tornadoes
Tornado outbreaks are days in which storms produce several tornadoes across the state and Illinois saw multiple outbreaks in February, March, and April. While there was only one tornado in May, well below the most recent 30-year average for that month, June more than made up for it with 80. July and August both had above average tornado frequency, bringing the 2026 total to 210 tornadoes at the start of September (Figure 1a).
The previous annual tornado record in Illinois was 142 in 2024. The all-time annual tornado record in the U.S. is held by Texas, which had 244 tornadoes in 2015. This year, Illinois has had more tornadoes than Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota, and Minnesota combined.
The five National Weather Service offices that serve Illinois have issued more than 1,300 severe thunderstorm and tornado warnings this year through Sept. 1, equating to one severe thunderstorm or tornado warning issue every 4.5 hours! The number of warnings issued this year so far exceeds the total in any previous entire year by more than 100 (Figure 1b).
Simply put, this year’s tornado frequency is truly remarkable and nothing like any other year on record in our state.
A New State Hail Record
The severe weather outbreak around the Kankakee area in March feels like ancient history by this time, but it was a record-breaking event. The storms produced 12 tornadoes and very large to gargantuan hail across a multi-county area between Pontiac and Kankakee and stretching into Indiana.
Among several gargantuan hailstones was one measuring 6.6 inches in maximum dimension, weighing 1.2 pounds, and with a volume of nearly 40 cubic inches (Figure 2). Did you know, gargantuan is the actual scientific term for hail measuring 6 inches or larger in its maximum dimension, according to the American Meteorological Society. The stone was collected by a family in Kankakee and was preserved perfectly until scientists from Northern Illinois University took the stone to their specialized lab for measurements.
A State Climate Extremes Committee assessed the potential record-breaking hailstone following the event. The committee voted unanimously to determine the Kankakee hailstone had set a new state record in maximum dimension, weight, and volume. The previous hail record dimension was held by a 4.75 inch stone that fell near Minooka in 2015.
NOAA produced a final report on the new state record hailstone.
What About Climate Change?
Illinois has experienced significant changes in its climate over the past century because of human-caused global warming. It is therefore completely reasonable to wonder if climate change is playing a role in such an excessive severe weather year like 2026. However, the impact of a warmer climate on severe weather in Illinois — severe thunderstorms, hail, and tornadoes — is less well understood than for other hazards like heatwaves and flooding.
Researchers have begun to address the complexity and uncertainty around severe weather response to climate change in Illinois. Here is a summary of what we know and don’t know currently, and references to associated studies that continue to improve our understanding of this important question:
- Storm environments that produce severe weather like strong winds, tornadoes, and large hail, have increased in Illinois over the past several decades1.
- Illinois has experienced more tornado outbreaks and very large hail in recent decades2,3.
- There remains uncertainty of the extent to which climate change is contributing to these recent trends in severe weather in Illinois, though it is thought the warmer and more humid climate in Illinois has had at least some effect on increasing severe storm environments4
- Climate models project increasing severe weather environments that can produce strong winds and tornadoes in future decades in Illinois.5,6
- Models also project a shift toward more severe storms in late winter and early spring in future decades, relative to our current and past climate.7
- Models show a potential for fewer hail events but more intense and severe hail in future decades.8
Importantly, the risk of impacts from severe weather is a consequence of both the hazard (i.e., the tornado, hail, etc.) and the underlying vulnerability of people and places affected by the hazard.
Regardless of potential increasing trends in severe storms, tornadoes, and hail, certain aspects of development can increase the risk of severe weather impacts, including loss of life. Many counties in southern Illinois have a disproportionately high risk of tornado fatalities and other impacts due to higher rates of poverty and a relatively high percentage of housing stock that is mobile homes9. Impact vulnerability is particularly high among immigrants and those for whom English is a second language, partly due to the lack of multilingual programming and disaster preparedness10.
It’s important to we continue to improve our severe weather communication, building and development safety, and hazard planning to be more resilient to severe weather now and into the future.
References
1 Gensini, V.A., and H.E. Brooks, 2018: Spatial trends in United States tornado frequency. npj Climate & Atmospheric Science, 1, 38, https://doi.org/10.1038/s41612-018-0048-2.
2 Moore, T.W., 2017: On the temporal and spatial characteristics of tornado days in the United States. Atmos. Res., 184, https://doi.org/10.1016/j.atmosres.2016.10.007.
3 Tang, B.H., Gensini, V.A., and C.R. Homeyer, 2019: Trends in United States large hail environments and observations. npj Climate & Atmospheric Science, 2, 45, https://doi.org/10.1038/s41612-019-0103-7.
4 Gensini, V.A., 2021: Severe convective storms in a changing climate. Climate Change and Extreme Events, Elsevier, 39-56, https://doi.org/10.1016/B978-0-12-822700-8.00007-X.
5 Allen, J., Gopalakrishnan, D., Cuervo-Lopez, C., Trapp, R., and Robinson, E. Comparing CMIP6 future projections for severe convective environments in a warming climate over Australia, Europe, and North America. 11th European Conference on Severe Storms, Bucharest, Romania, May 8, 2023, https://doi.org/10.5194/ecss2023-160, 2023.
6 Haberlie, A.M., Ashley, W.S., Battisto, C.M., and V.A. Gensini, 2022: Thunderstorm activity under intermediate and extreme climate change scenarios. Geophys. Res. Lett., https://doi.org/10.1029/2022GL098779.
7 Ashley, W.S., Haberlie, A.M., and V.A. Gensini, 2023: The future of supercells in the United States. Bull. Amer. Meteorol. Soc., 104, https://doi.org/10.1175/BAMS-D-22-0027.1.
8 Raupach, T.H., and coauthors, 2021: The effects of climate change on hailstorms. Nature Reviews Earth & Environment, 2, https://doi.org/10.1038/s43017-020-00133-9.
9 Strader, S.M., and W.S. Ashley, 2018: Finescale assessment of mobile home tornado vulnerability in the central and southeast United States. Weather, Climate, & Society, 10, https://doi.org/10.1175/WCAS-D-18-0060.1.
10 Trujilo-Falcón, J.E., Pabón, A.G., Reedy, J., and Klockow-McClain, K.E., 2022: Systemic Vulnerabilities Created an Informal Warning System for U.S. Hispanic and Latinx Immigrants in the 2021 Quad-State Tornado Outbreak. Natural Hazards Review, https://doi.org/10.31223/X5FW8F.