An intense heat wave sweeping the desert Southwest has pushed more people into emergency rooms across the Phoenix area, health officials and emergency physicians say. Temperatures approaching 115 degrees have produced a spectrum of heat-related problems, from simple dehydration to dangerous, life-threatening heat stroke. While city officials report that heat-related deaths have stabilized or fallen slightly in recent years, clinicians on the front lines describe a broader, ongoing public-health strain driven by longer, hotter summers.
Shows: U.S. map of heat-related emergency-department visits per 100,000 people for the week of July 2–8, 2023, showing the Southwest — including Arizona — with the highest rates and illustrating the public‑health toll of extreme heat.
Dr. Paul Pugsley, who serves as emergency department medical director for Valleywise Health in Phoenix, described an influx of patients presenting with a wide range of heat-related ailments. "It occurs because your skin and blood vessels are dilating in response to heat as you try and sweat, to heat cramps from people who are mildly dehydrated, and then all the way up to severe heat stroke where people have neurologic dysfunction, and we see everything in between," he said. Those clinical observations paint a picture of emergency rooms treating not only straightforward heat exhaustion but also complications that require urgent, and sometimes prolonged, medical care.
Among the conditions being aggravated by the high temperatures are chronic illnesses that are already prevalent in the community. Pugsley noted that underlying problems such as heart disease, asthma and certain mental illnesses can be worsened by extreme heat, increasing the risk of hospitalization for patients who otherwise might manage their conditions. The interaction between chronic disease and heat exposure means that the vulnerable in the population are not limited to one demographic group: younger people with chronic illnesses can be as susceptible as older adults who are generally less robust in the face of extreme temperatures.
The physician emphasized that particular segments of the population face heightened risk. "Those who are most at risk are the very young and the very old," Pugsley said, specifically naming children under two years of age and adults over 60. He added, however, that age alone is not the only determinant of danger: individuals of any age who have chronic medical problems can be at elevated risk when exposed to prolonged heat. Low-income residents and people without stable housing are especially exposed because they often lack reliable access to cooling and shade, or to regular medical care that can identify and treat early signs of heat-related illness.
The strain on emergency services is not only clinical but logistical. Hospital emergency departments are seeing patients who present with severe heat rash, cramps and dehydration, but they must also triage and treat people whose neurological function has been impaired by heat stroke — a condition that requires careful monitoring and, in some cases, intensive supportive care. The range of presentations means emergency staff must be prepared for both high volumes of relatively mild cases and the intermittent but severe cases that can lead to long hospital stays or intensive interventions.
Shows: Illustration of a thermometer, ambulance and cooling fans representing rising heat-related illnesses and increased emergency responses as extreme Arizona temperatures strain health services.
City leaders in Phoenix are responding by expanding public cooling options intended to reduce the immediate risk to unhoused and low-income residents. The city is working to open additional cooling stations across Phoenix and has recently inaugurated its first overnight facility downtown to provide a place for people to escape the heat. Officials framed these measures as part of a broader push to reduce heat exposure among those who have the fewest resources to cope with extreme temperatures, aiming to prevent the kinds of preventable emergency visits that fill hospital corridors during peak heat.
Emergency department clinicians like Pugsley say the lines they are seeing in treatment rooms reflect a changing reality. Even with a reported leveling or slight decline in heat-related fatalities over recent years, the longer duration and increased intensity of summer heat are producing a steady flow of patients whose illnesses and underlying conditions are exacerbated by the climate. For hospitals and city services, that means continuing to adapt capacity and outreach efforts to address both acute medical needs and the social factors that leave some residents particularly exposed to the season’s extremes.
Preliminary 2025 data released by Governor Katie Hobbs show Arizona heat-related deaths falling to 667 from 997 in 2024, alongside a decline in emergency department visits after years of increases, per the Arizona Department of Health Services. In Maricopa County, which includes Phoenix, deaths dropped to 427 from 608 the prior year, marking a second straight decline as cooling centers and workplace protections expand.
The governor’s news release notes that more than 46,600 people are subscribed to heat alerts from the Arizona Department of Health Services, a notification effort the state has highlighted as part of its heat-response strategy.
Governor Katie Hobbs issued an executive order directing the Arizona Division of Occupational Safety and Health to form a Workplace Heat Safety Task Force and to build on a Heat Stress State Emphasis Program launched in July 2023 to strengthen workplace protections.
Valleywise Health and collaborators have developed and published an in‑emergency‑department cold‑water immersion protocol for treating severe heatstroke, a rapid‑cooling approach that Phoenix clinicians have implemented to improve outcomes in critical cases.
The Arizona Department of Health Services released an updated 2025 “Strategies and Approaches” guidance document that includes county‑level heat trends and public‑health recommendations to support local planning and response.