This year, Milwaukee saw one of its warmest-ever summers — thanks in no small part to several stretches of sweltering heat nearing triple-digit temperatures.
Milwaukee's summer heat came amid warming temperatures globally due to climate change: 2023 was the world's hottest year on record , and a recent report found more Americans died from heat in 2023 than any other year in over two decades of records.
The toll of this summer's heat on illnesses and deaths is not yet clear, but early numbers on 2024 hospital visits in Wisconsin paint a grim picture.
As of early September, the number of Wisconsin emergency department (ED) visits from heat was about 25% higher than last year, according to data provided by Dr. Sheryl Bedno, chief medical officer in the Wisconsin Department of Health Services' Bureau of Environmental and Occupational Health.
Here's how heat illness this summer compared to previous years and which parts of Wisconsin were the most affected.
Heat emergency department visits reach highest level since 2018
After five years of heat-related ED visits totaling about 800 visits or under, the number of ED visits from heat reached 1,056 in Wisconsin this year, as of Sept. 2, according to data provided by DHS.
That's the highest since 2018, when 1,131 Wisconsinites visited the ED for heat illness. The 2024 data is not yet final, but includes reporting from about 95% of Wisconsin's emergency departments, according to DHS.
The number of ED visits peaked four different times throughout the summer — all of them periods when Milwaukee and the rest of the state were experiencing excessive heat. The end of August logged the highest number of visits, with more than 70 Wisconsinites needing emergency treatment on Aug. 26 .
From July 13 to 15, close to 40 Wisconsinites visited the ED every day for heat illness.
July 15 also marked the first day of the Republican National Convention , which saw about 50,000 people milling about in downtown Milwaukee. The convention kicked off with nearly 90-degree heat, with the Milwaukee Fire Department responding to a dozen heat-related calls on the first day of the RNC.
It's worth noting DHS data excludes non-Wisconsin residents, so any heat-related ED visits from out-of-state visitors during the RNC are not included in the 1,056 total. The data does, however, include Wisconsinites who visited the ED in Iowa and Minnesota.
ED visits also peaked to about 30 per day in late June and to more than 45 in a single day on July 31 .
Are hospitalizations from heat rising?
Hospitalization data from heat in 2024 is not yet available, but that number has remained steady at about 70 hospitalizations or below since 2019.
However, like ED visits, hospitalizations last peaked in 2018, with 82 Wisconsinites hospitalized for heat that year. If the trend with 2024 ED visit data is any indicator, perhaps another spike in hospitalizations is on the horizon.
Hospitalization data for summer 2024 will take several months to process, according to DHS.
Are heat deaths getting worse in Wisconsin?
Though the country experienced a historic surge in heat deaths last year, Wisconsin actually saw a decrease in heat deaths last year — but take these numbers with the grain of salt. The 2023 death data is not yet final and subject to change, and 2024 data is not yet available, according to DHS.
In general, heat deaths have been rising in Wisconsin for nearly a decade.
After a peak of 24 deaths in 2012, the number dropped significantly to one death in 2014. Since then, however, fatalities have began ticking back up.
In 2022, 15 Wisconsinites died from heat, marking the highest number of deaths in 10 years.
Which parts of Wisconsin saw the most heat illness?
The southeast region of Wisconsin saw the most heat-related ED visits this summer — likely because of the large population in this part of the state, which includes Milwaukee, Bedno said in a statement.
According to Emergency Medical Services (EMS) response data, the northwest region of the state actually saw the highest number of heat-related EMS runs proportional to its population. This region, which includes Eau Claire and Menomonie, saw 14.8 responses for every 10,000 residents.
The southwest was the second-highest at 11.7 responses for every 10,000 residents.
Why heat illnesses and deaths go underreported
In general, Bedno said it's worth taking all this data with the caveat that heat illnesses and deaths often go underreported. Heat frequently triggers or coincides with symptoms of other illnesses, meaning heat exposure is sometimes not formally logged as a cause of illness or death.
Additionally, some people with heat illness may not seek medical care at all, either because their symptoms are mild or because those most at risk of heat illness are also more likely to face barriers to health care.
The latter includes people who do not have health insurance, people without transportation or funds to reach a hospital, people with disabilities, and low-income and racially marginalized people.
Experts have long warned that historically marginalized communities will bear the brunt of climate change's harms, including increasingly severe heat. In a 2020 report , the Centers for Disease Control and Prevention found non-Hispanic Native Americans had the highest rate of heat-related deaths in the country, followed by non-Hispanic Black Americans.
More: Summer 2024 was one of Milwaukee's warmest in history, setting multiple records
This article originally appeared on Milwaukee Journal Sentinel: Emergency department visits from heat rose 25% in Wisconsin in 2024
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