June 29, 2023
Climate Shift Index™ alert
Climate Central analysis shows that human-caused climate change is making the dangerous heat in the West at least 5 times more likely.
Forecast
Forecasts indicate a 3-day stretch of anomalous and extreme heat is expected across California and the rest of the West from Saturday, July 1 through Monday, July 3, 2023.
Daytime temperatures are forecast to approach 110°F in several cities in California and are expected to exceed these levels in parts of Nevada and Arizona.
Attribution Science
Daily average temperatures during the event are expected to exceed Climate Shift Index (CSI) levels of 2 across a broad region stretching from California to Colorado. Places in five states (California, Nevada, Arizona, Colorado, Utah) will reach Level 5 which indicates that human-caused climate change made this excessive heat at least 5 times more likely.
Health, Safety and Impact Risks
These temperatures could present heat safety risks, particularly given the rapid increase in temperatures following a cooler-than-average start to the summer.
Humans, wildlife, and plants including valuable agricultural crops have not had a chance to acclimate to warmer temperatures and may experience extra stress due to the rapid onset of the event.
Populations most vulnerable to high temperatures include older adults, young children, pregnant women, individuals with chronic conditions, members of low income and historically marginalized communities, athletes, and outdoor workers.
For more information on heat and the related human health implications refer to our Climate Matters brief, More Risky Heat Days in 232 U.S. Locations, which found a significant increase in annual days above local risky heat thresholds in several California cities. Compared to 1970, Fresno now experiences 36 more risky heat days per year. Other cities of note in the event: Chico (18 more), Sacramento (10 more), Bakersfield (8 more), Las Vegas (39 more), and Phoenix (32 more risky heat days).
Quotes
Dr. Andrew Pershing, VP of Science at Climate Central, said:
“This weekend, millions of people across five states will experience unusual heat. Human-caused climate change made this event more likely and more intense.”
To request an interview with a Climate Central scientist, please contact Peter Girard at pgirard@climatecentral.org
Reporting resources
Exposure to risky heat can trigger heat-related illnesses, including heat exhaustion and heat stroke, a life-threatening condition. For more information on heat safety, visit the National Integrated Heat Health Information System’s Planning and Preparing guide.
The U.S. Climate Shift Index map tool has free maps showing the fingerprint of climate change on local average, maximum, and minimum temperatures.
The influence of climate change on daily average temperatures across the globe is available on the global Climate Shift Index map.
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, and a summary of the connection between heatwaves and climate change from Yale Climate Connections.
About the Climate Shift Index
Climate Central’s Climate Shift Index, grounded in the latest peer-reviewed science, maps the influence of climate change on temperatures across the globe, every day.
Climate Shift Index levels indicate how much human-caused climate change has altered the frequency of daily temperatures at a particular location. Level 1 indicates that climate change is detectable in that day’s temperature. Level 2 means that climate change made exceptionally warm temperatures in a given location at least twice as likely. Level 5 is the maximum and indicates temperatures at least 5 times more likely because of climate change.
For this analysis, temperatures come from NOAA’s Global Forecast System model.
About the Climate Shift Index ™
Climate Central’s Climate Shift Index ™, grounded in the latest peer-reviewed science, maps the influence of climate change on temperatures across the globe, every day.
Climate Shift Index ™ levels indicate how much human-caused climate change has altered the frequency of daily temperatures at a particular location. Level 1 indicates that climate change is detectable in that day’s temperature. Level 2 means that climate change made exceptionally warm temperatures in a given location at least twice as likely. Level 5 is the maximum and indicates temperatures at least 5 times more likely because of climate change.
For this analysis, temperatures come from NOAA’s Global Forecast System model.