Climate Shift Index Alert•June 17, 2024

Intense, persistent heat wave across Midwestern and Eastern U.S. influenced by climate change

From June 18-20, over 25 million people in the eastern half of the U.S. will experience heat made at least four times more likely because of human-caused climate change. This week is a continuation of the intense, persistent heat that has already been experienced by much of the Midwestern and Eastern United States.

Note: This event is forecast to continue beyond June 20. Use the Global Climate Shift Index map to stay updated on heat in your region.

CSI Alert Graphic (Eastern US) June 18-20, 2024 EN

How unusual is the forecasted heat?

  • The high-pressure system, which has caused excessive heat across the Southwestern U.S. for several weeks, will shift to create a large heat dome over the eastern half of the country.

  • From Tuesday, June 18, through Thursday, June 20, a multi-day “major” to “extreme” heat event is expected to impact millions of people in states spanning from Iowa to Maine.

  • Record-level high temperatures of 94°F to 99°F are forecast in major metropolitan areas including Indianapolis, Cleveland, Detroit, Pittsburgh, Philadelphia, Washington D.C., New York City, and Boston.

  • This heat, combined with elevated humidity, will result in heat index values reaching 105°F for states including Illinois, Indiana, Michigan, Ohio, West Virginia, Pennsylvania, New York, Connecticut and Massachusetts.

  • Nighttime temperatures are forecast to remain 10°F to 15°F above average, in the 70°F to 76°F range, which may break records across the Lower Midwest.

How has climate change influenced this extreme heat?

  • Daily average temperatures are expected to reach Climate Shift Index (CSI) levels of 4 in much of West Virginia, Ohio, and Indiana. A CSI level 4 indicates that human-caused climate change made this excessive heat at least four times more likely, signifying an extreme climate change event. 

  • Over the entire period, 25 million people in the eastern half of the U.S. will experience at least one day with CSI level 4.

Many cities will experience extended periods of extreme heat. See table below for cities most impacted. 

Use the Climate Shift Index global map to see CSI levels in your city and region, and see our FAQs to learn about the CSI in both English and Spanish. 

City

State

Date of peak temperature anomaly


Peak temperature anomaly (°F above normal)

Maximum temperature that day (°F)

CSI level that day

Days at or above CSI = 3, (June 18-20)

Average CSI, (June 18-20)

Portland

Maine

June 20

15.9

86.4

4

2

2.7

Canton

Ohio

June 20

13.1

93.5

4

3

3.3

Toledo

Ohio

June 19

12.8

93.3

3

1

2.3

Youngstown

Ohio

June 18

12.1

93.3

3

1

2.3

Fort Wayne

Indiana

June 19

11.8

92.9

4

3

3.7

Pittsburgh

Pennsylvania

June 18

11.4

92.3

5

3

3.7

Dayton

Ohio

June 19

10.7

90.9

4

3

3.7

Wheeling

West Virginia

June 20

10.6

90.7

3

3

3.3

Indianapolis

Indiana

June 20

10.1

95.2

5

3

3.7

Charleston

West Virginia

June 18

9.9

95.0

5

3

4.3

Table 1. Selection of cities with significant temperature anomalies (departure from normal temperatures) with a climate change signal (CSI level 3 or higher) on certain dates during June 18-20, 2024. The peak temperature anomalies and CSI levels are based on the average daily anomaly for that city. The average CSI for June 18-20, 2024 refers to the CSI level for the 3-day period as a whole. 

What impact could this heat have?

  • This severity of dangerous extreme heat can affect anyone without access to effective cooling measures and/or adequate hydration, including healthy adults, but can have disproportionate effects on young children, elderly persons living alone, emergency and outdoor workers, and the medically uninsured.

  • The urban heat island effect can add more than 8°F to these temperatures in the urban core, particularly those underserved neighborhoods lacking sufficient tree cover and/or green space. 

  • Those planning to participate in outdoor celebrations for the Juneteenth holiday will be exposed to an elevated risk of heat illnesses and should confirm access to cooling options prior to attendance.

  • Excessively warm nighttime temperatures provide little to no heat relief and may exacerbate negative heat-related health impacts, including sleep loss. Insufficient sleep can compromise immune system functioning, increase risk for cardiovascular disease, and harm cognitive performance. 

What do experts say?

Dr. Andrew Pershing, VP of Science at Climate Central, said: “Human-caused climate change makes the heat season start earlier and makes heat waves hotter and more dangerous. Until we stop burning coal, oil, and natural gas, conditions like this week's dangerous heat will become more and more common.”

How do we know climate change is influencing this heat?

The Climate Shift Index uses peer-reviewed methodology to estimate how climate change has increased the likelihood of a particular daily temperature. It can be run using historical or forecast temperatures.

Using computer models, we compared the likelihood that these temperatures would occur in a world without carbon emissions released by humans, versus in today's world with decades of carbon emissions building up in the atmosphere. This is an established scientific method to determine how much climate change has or has not affected individual extreme weather events.

For this analysis, temperatures come from the National Center for Environmental Prediction’s Global Forecast System.

To request an interview with a Climate Central scientist, please contact Peter Girard at pgirard@climatecentral.org

Reporting resources

Until carbon emissions end, heat waves everywhere will continue to become hotter and more dangerous. Explore quick facts and local analyses on the links between climate change and extreme heat in: