Climate Shift Index Alert•June 4, 2024
Climate change influencing early-season extreme heat across North America
Between June 5-7, much of the Western United States, Mexico, and Eastern Canada are poised to experience a period of unusually hot conditions made much more likely because of human-caused climate change. During this period, over 229 million people across North America will experience extreme heat made at least three times more likely because of human-caused climate change.
Note: This event is an extension of ongoing heat in Mexico and around the Gulf of Mexico, and it may continue beyond June 7 in some locations. Use the Global Climate Shift Index map to stay updated on heat in your region.
How unusual is the forecasted heat?
Large parts of the Western United States are forecast to face “major” to “extreme” heat from Wednesday, June 5, through Friday, June 7. Excessive heat watches and warnings have been issued for California’s Sacramento and San Joaquin Valleys and across the Desert Southwest.
The prolonged extreme heat, which has persisted for over a month in Mexico, will expand north as a large area of high pressure intensifies over the Western U.S. due to a blocking low pressure system in the Pacific Ocean.
Widespread daytime temperatures exceeding 105°F (40.6°C) are expected, with maximum temperatures forecast to surpass 110°F (43.3°C) in major metropolitan areas, including Las Vegas and Phoenix.
The urban heat island effect can add more than 8°F to these temperatures in urban environments, particularly in underserved neighborhoods lacking sufficient tree cover and/or green space.
How has climate change influenced this heat?
Daily average temperatures are expected to reach Climate Shift Index (CSI) levels of 5 in the southwest U.S. and Mexico. Additionally, the unusually warm temperatures in Quebec and Newfoundland and Labrador will reach CSI level 5. A CSI level 5 indicates that human-caused climate change made this excessive heat at least five times more likely, signifying an exceptional climate change event.
Between June 5-7, over 229 million people across North America will experience at least one day with CSI level 3, while about 181 million people will experience at least one day with CSI level 5.
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 | Country | Date of peak temperature anomaly | Forecast peak temperature anomaly (°F above normal) | Forecast high temperature (°F ) | Maximum CSI level | Forecast days at or above CSI = 3, June 5-7 | Forecast average CSI, June 5-7 |
|---|---|---|---|---|---|---|---|
Havana | Cuba | June 7 | 2.4 | 89.9 | 5 | 3 | 4.3 |
Santo Domingo | Dominican Republic | June 5 | 4.0 | 87.1 | 5 | 3 | 5.0 |
Santiago | Dominican Republic | June 5 | 1.7 | 87.6 | 5 | 1 | 2.7 |
Guatemala City | Guatemala | June 5 | 5.7 | 83.3 | 5 | 3 | 5.0 |
Mexico City | Mexico | June 5 | 7.3 | 84.6 | 5 | 3 | 5.0 |
Guadalajara | Mexico | May 6 | 5.2 | 98.0 | 5 | 3 | 4.7 |
Tijuana | Mexico | June 7 | 9.3 | 78.2 | 4 | 1 | 2.3 |
Ecatepec | Mexico | June 5 | 6.9 | 86.9 | 5 | 3 | 5.0 |
Ciudad Nezahualcóyotl | Mexico | June 5 | 6.9 | 86.9 | 5 | 3 | 5.0 |
Leon de los Aldama | Mexico | June 6 | 5.6 | 97.1 | 5 | 3 | 5.0 |
Puebla | Mexico | June 6 | 6.3 | 87.0 | 5 | 3 | 5.0 |
Zapopan | Mexico | June 6 | 4.5 | 98.8 | 5 | 3 | 4.3 |
Juarez | Mexico | June 7 | 9.4 | 103.2 | 5 | 3 | 4.3 |
Monterrey | Mexico | June 5 | 8.7 | 103.8 | 5 | 3 | 5.0 |
Mexicali | Mexico | June 7 | 12.8 | 113.6 | 4 | 2 | 2.7 |
Villahermosa | Mexico | June 5 | 8.0 | 107.6 | 5 | 2 | 4.0 |
Los Angeles | U.S. | June 7 | 3.4 | 75.9 | 1 | 0 | 1.0 |
Miami | U.S. | June 7 | 4.0 | 87.5 | 5 | 3 | 4.7 |
Dallas | U.S. | June 6 | 4.6 | 94.0 | 2 | 0 | 0.7 |
Philadelphia | U.S. | June 6 | 8.4 | 85.5 | 1 | 0 | 0.3 |
Houston | U.S. | June 7 | 5.3 | 96.7 | 5 | 3 | 4.0 |
Atlanta | U.S. | June 6 | 3.3 | 85.5 | 1 | 0 | 0.3 |
Washington | U.S. | June 6 | 9.7 | 91.9 | 2 | 0 | 0.7 |
Phoenix | U.S. | June 7 | 11.4 | 111.2 | 5 | 3 | 4.3 |
Seattle | U.S. | June 7 | 3.0 | 71.5 | 1 | 0 | 0.3 |
San Francisco | U.S. | June 5 | 1.5 | 63.9 | 1 | 0 | 0.3 |
San Diego | U.S. | June 7 | 10.2 | 85.6 | 3 | 1 | 2.0 |
Tampa | U.S. | June 6 | 3.8 | 89.7 | 5 | 3 | 4.3 |
Denver | U.S. | June 7 | 8.5 | 88.0 | 2 | 0 | 1.7 |
Riverside | U.S. | June 7 | 11.0 | 93.0 | 2 | 0 | 2.0 |
Baltimore | U.S. | June 6 | 9.8 | 87.0 | 4 | 1 | 1.7 |
Las Vegas | U.S. | June 6 | 14.0 | 103.9 | 5 | 3 | 5.0 |
Portland | U.S. | June 7 | 8.2 | 84.8 | 1 | 0 | 0.3 |
San Antonio | U.S. | June 5 | 9.2 | 103.0 | 5 | 3 | 4.7 |
Sacramento | U.S. | June 5 | 18.6 | 105.2 | 3 | 1 | 2.0 |
Orlando | U.S. | June 7 | 4.7 | 97.2 | 5 | 3 | 4.3 |
San Jose | U.S. | June 5 | 15.1 | 90.7 | 1 | 0 | 1.0 |
Austin | U.S. | June 5 | 7.8 | 100.2 | 5 | 3 | 4.0 |
Charlotte | U.S. | June 6 | 6.1 | 91.1 | 2 | 0 | 0.7 |
Virginia Beach | U.S. | June 6 | 8.3 | 84.1 | 2 | 0 | 1.3 |
Jacksonville | U.S. | June 7 | 8.1 | 96.9 | 5 | 3 | 4.3 |
Salt Lake City | U.S. | June 7 | 17.8 | 92.9 | 5 | 2 | 3.3 |
Richmond | U.S. | June 6 | 10.1 | 94.2 | 2 | 0 | 0.7 |
New Orleans | U.S. | June 7 | 3.5 | 88.8 | 2 | 0 | 2.0 |
What impact could this heat have?
This level of extreme heat can affect anyone without access to effective cooling measures and/or adequate hydration — including healthy adults — but can have disproportionate effects on others, including elderly people living alone, people with disabilities, emergency and outdoor workers, and residents of substandard housing.
Nightime temperatures are forecast to remain in the 75°F to 85°F (23.9°C to 29.4°C) range. These conditions will provide little to no overnight relief and may exacerbate negative heat health impacts.
The melting of mountain snowpack may introduce dangerously cold and fast moving water to rivers and lakes which can threaten the safety of those seeking relief from heat in local waterways. Exposure to cold water can lead to bodily incapacitation within several minutes.
What do experts say?
Dr. Andrew Pershing, VP of Science at Climate Central, said: “This is really a continental scale event. Hundreds of millions of people will experience heat that was made more likely and more intense by human-caused climate change.”
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 greenhouse gas emissions end, heatwaves 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:
Climate Central’s Extreme Weather Toolkit: Extreme Heat
World Weather Attribution’s guide to reporting on extreme heat and climate change
Yale Climate Connections’ summary of the connection between heat waves and climate change.