Extreme Events

Our Changing Extremes

Since 1916, the amount of rain that falls during the annual largest storm in Minnesota has increased by more than an inch.

Not only has the yearly maximum rain event become more extreme, but some extreme events have become more common. A catastrophic "mega-rain event'' occurs when at least six inches of rain fall over an area of at least 1,000 square miles. Between 1973 and 2020, there were 17 mega-rain events in Minnesota, with almost two times as many happening in the 21 years between 2000 and 2020 as happened in the 27 years between 1973 and 1999. 

Projected change in heavy precipitation

The average number of days per 100 years when daily rainfall exceeds 4 inches in Minnesota. The plot on the left shows the present day (1981-2010), the plot in the middle shows the end of  the 21st Century (2081-2100) for the RCP4.5 emissions scenario, and the plot on the right shows the end of  the 21st Century (2081-2100) for the RCP8.5 emissions scenario. RCP4.5 assumes that emissions peak in the mid-20th Century (about 2040) and then decline, such that CO2 concentrations in the atmosphere are steady by 2100. RCP8.5 assumes that emissions don’t decline and CO2 concentrations in the atmosphere increase through 2100.
(Maps modified from University of Wisconsin Probabilistic Downscaling v2.0. | David Lorenz and the Nelson Institute Center for Climatic Research.)

 

 

A heatwave can be defined as a series of at least 4 days with air temperatures that would normally only occur about once every 10 years. So far there is no evidence of increasing very hot days in Minnesota, but these days are projected to become more frequent under different climate change scenarios. Climate change might make heat waves stronger and longer. As the average temperature goes up, the same relative increase in temperature during a heat wave would result in a hotter absolute temperature. For example, if a region's average temperature in July is 75 degrees Fahrenheit and a typical heatwave is when the temperature is 15 degrees Fahrenheit above normal, then the heatwave temperature is about 90 degrees Fahrenheit. But if the region's average July temperature increases to 80 degrees Fahrenheit, then a similar increase of 15 degrees Fahrenheit would result in a heatwave of 95 degrees Fahrenheit. This also doesn't account for a possible "tipping point", where moving into a new temperature range can result in a much larger change in heat waves. As the climate warms, heat waves will get excessively hotter.  

Average number of days per year when the temperature exceeds 100 degrees F

The average number of days per year when temperature exceeds 100℉ in Minnesota. The plot on the left shows the present day (1981-2010), the plot in the middle shows the end of  the 21st Century (2081-2100) for the RCP4.5 emissions scenario, and the plot on the right shows the end of  the 21st Century (2081-2100) for the RCP8.5 emissions scenario. RCP4.5 assumes that emissions peak in the mid-20th Century (about 2040) and then decline, such that CO2 concentrations in the atmosphere are steady by 2100. RCP8.5 assumes that emissions don’t decline and CO2 concentrations in the atmosphere increase through 2100.
(Maps modified from University of Wisconsin Probabilistic Downscaling v2.0. | David Lorenz and the Nelson Institute Center for Climatic Research.)

Consequences

flood

Extreme precipitation can increase flooding, leading to contamination of recreational and drinking water sources.

hospital

Extreme heat events can exacerbate pre-existing chronic conditions such as cardiovascular, respiratory, liver, & neurological diseases, endocrine disorders, & renal disease or failure.

mold on door

Flooding can also directly affect human health by damaging health care facilities, promoting mold growth in homes, or causing death by drowning.

Expand all

References & Suggested Reading

Ebi KL, Balbus J, Kinney PL, Lipp E, Mills D, O’Neill MS, and Wilson M. 2008. Effects of global change on human health. In: Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems [Gamble JL (editor), Ebi KL, Sussman FG, and Wilbanks TJ (authors)]. Synthesis and Assessment Product 4.6. U.S. Environmental Protection Agency, Washington, DC, pp. 39-87.

Federal Emergency Management Agency (FEMA). 2021. "Ready: Floods". url: http://www.ready.gov/floods. Accessed Aug 18, 2021

Great Lakes Integrated Sciences and Assessments. url:glisa.umich.edu. Accessed July 16, 2021. 

Harding, K. J., and P. K. Snyder (2014), Examining future changes in the character of Central U.S. warm-season precipitation using dynamical downscaling, J. Geophys. Res. Atmos., 119, doi:10.1002/2014JD022575.

Harding, K. J., and P. K. Snyder (2015), Using dynamical downscaling to examine mechanisms contributing to the intensification of Central U.S. heavy rainfall events, J. Geophys. Res. Atmos., 120, doi:10.1002/2014JD022819.

Melillo J., Richmond, T., and Yohe, G., 2014. An assessment from the U.S. Global Change Research Program to inform the public with scientific information and methods regarding climate change.

USGCRP, 2018: Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 1515 pp. doi: 10.7930/NCA4.2018.