As California grapples with rising temperatures due to climate change, a new study reveals a significant increase in emergency room (ER) visits linked to hotter summers, placing a growing burden on the state’s healthcare system. Published on July 30, 2025, in Science Advances, the research highlights how extreme heat is making Californians sicker in unexpected ways, particularly affecting young children and straining medical infrastructure. Here’s what you need to know about this alarming trend and its implications for public health.

Key Findings from the Study

The study, led by Carlos Gould, Ph.D., an environmental health scientist at the University of California San Diego, analyzed 123 million ER visits, 45 million hospital admissions, and 2.9 million death records in California from 2006 to 2017. Key findings include:

• ER Visits Surge with Heat: Emergency room visits increase linearly as temperatures rise, with a 0.46% increase (1.5 million additional visits) projected by 2050 under moderate climate change scenarios.
• Children Most Affected: Children under 5 are visiting ERs at higher rates than any other age group, with conditions like respiratory issues, poisonings, and nervous system problems linked to heat.
• Fewer Cold-Related Deaths: While extreme heat and cold both increase mortality, particularly among older adults, the decline in extreme cold days is expected to reduce overall temperature-related deaths by 53,500 annually by 2050, saving approximately $30 billion.
• Economic Impact: The rise in ER visits is projected to cost California an additional $52 million annually by 2050, though hospitalization costs may decrease by $53 million.

“Hot days can worsen our health far before they lead to deaths,” said Gould. “And it can be a large range of things that we get sick from.”

Why Heat Is Driving ER Visits

The research points to a variety of heat-related illnesses contributing to the ER surge, including:

• Respiratory and Nervous System Issues: Higher temperatures exacerbate conditions like asthma and neurological disorders.
• Poisonings and Injuries: Heat may influence behavior, leading to increased incidents of poisonings and injuries, though the exact mechanisms remain unclear.
• Vulnerable Populations: Children are particularly susceptible due to their physiology, such as a higher surface-area-to-body-mass ratio and lower sweat production, making it harder for them to regulate body temperature.

Kristie Ebi, a professor at the University of Washington, emphasized the public health challenge: “It remains problematic to trade off mortality and morbidity from hot versus cold temperature extremes. The goal of public health is to prevent as much morbidity and mortality as possible.”

Implications for California’s Healthcare System

The study underscores the need for hospitals, insurers, and public health agencies to prepare for increased demand during heatwaves. With ER visits rising sharply, particularly for non-fatal conditions like mental health issues, endocrine disorders, and digestive problems, California’s healthcare infrastructure faces significant strain. The researchers suggest tailoring warnings and resources to different age groups, with a focus on protecting vulnerable populations like children and outdoor workers.

By 2100, the study projects a 0.76% increase in ER visits, further highlighting the long-term challenges of climate-fueled warming. Alexandra Heaney, Ph.D., co-author of the study, noted, “We need to focus on the full spectrum of health impacts when we think about heat waves, now and in the future.”

National Context and Broader Trends

While the study focuses on California, its findings align with national trends. A 2023 CDC report found that heat-related ER visits spiked across the U.S. during the warm months, with nearly 120,000 visits recorded, 90% occurring between May and September. Men and adults aged 18–64 were particularly affected, with regions like Arkansas, Louisiana, and Texas seeing the highest rates.

As global warming intensifies, experts warn that hotter summers will become more frequent, exacerbating health risks. The U.S. Environmental Protection Agency notes that heatwave seasons are now 49 days longer than in the 1960s, a trend expected to worsen without significant action to reduce greenhouse gas emissions.

What Can Be Done?

Public health officials are urged to broaden their approach to heatwave preparedness. Recommendations include:

• Enhanced Public Health Messaging: Issue targeted heat warnings for vulnerable groups, such as children and the elderly.
• Cooling Centers and Resources: Expand access to cooling centers and hydration stations in urban areas.
• Healthcare System Preparedness: Increase ER staffing and supplies during summer months to handle the influx of patients.
• Climate Action: Reduce greenhouse gas emissions to mitigate the frequency and intensity of heatwaves.

NOAA’s Heat and Health Tracker and other tools are helping communities identify high-risk areas and implement resilience measures, such as urban heat-mapping to locate and cool the hottest spots.

Conclusion

As California faces hotter summers, the rise in emergency room visits signals a growing public health crisis. The Science Advances study highlights the urgent need to address the full spectrum of heat-related illnesses, from respiratory issues to unexpected conditions like poisonings. By preparing healthcare systems and implementing proactive measures, California can better protect its residents from the health impacts of a warming planet.

For more information on how climate change is affecting public health, visit ClickUSANews.com for the latest updates.

Keywords: hotter summers, California emergency room visits, heat-related illnesses, climate change health impacts, public health, ER surge, California healthcare system