Overdose Spike Alert: Extreme Heat Increases Drug Overdose Risk in Wisconsin

Public Health Madison & Dane County has issued an urgent health alert following a sharp increase in suspected opioid overdoses linked to extreme summer heat. At least seven suspected opioid-involved overdoses were reported on June 29 and 30, 2026 — significantly more than typically seen in this community over a two-day period.

This alert highlights a growing but often overlooked danger: the deadly interaction between high temperatures and substance use. As heat waves become more frequent and intense across the United States, understanding this risk — and how to mitigate it — can save lives.

What Happened in Dane County

On July 1, 2026, Public Health Madison & Dane County issued a public health alert after first responders reported at least seven suspected opioid-involved overdoses and several related incidents during the final two days of June. This spike coincided with a period of extreme heat in the region.

The alert represents an important shift in how public health departments are approaching overdose prevention: recognizing that environmental factors like temperature can significantly amplify the risks of substance use.

"There are steps you can take to protect yourself including using less or going slow, using a buddy system, not using in a parked car, and always carrying naloxone in case of an overdose," said Public Health Supervisor Julia Olsen in the department's announcement.

The Science: Why Heat Makes Drug Use More Dangerous

The connection between extreme heat and increased overdose risk is well-documented in medical literature, though it remains underrecognized by the general public.

How Opioids Affect Temperature Regulation

Opioids — including heroin, fentanyl, and prescription pain medications — interfere with the body's ability to regulate temperature. They can:

• Reduce sweating, the body's primary cooling mechanism
• Lower blood pressure, making it harder to circulate blood to the skin for heat dissipation
• Cause dehydration through reduced fluid intake and increased fluid loss
• Depress the central nervous system, compounding respiratory depression during overdose

When combined with extreme heat, these effects create a dangerous scenario where the body cannot cool itself effectively, leading to heat exhaustion or heat stroke — conditions that can be fatal on their own, even without overdose.

Stimulants and Heat: A Different but Equal Danger

Stimulants like cocaine and methamphetamine pose the opposite but equally serious problem: they raise body temperature and heart rate while constricting blood vessels. In hot weather, this can quickly lead to:

• Hyperthermia (dangerously high body temperature)
• Cardiovascular stress and heart arrhythmias
• Dehydration and electrolyte imbalances
• Rhabdomyolysis (muscle breakdown that can damage kidneys)

The Alcohol Factor

Mixing drugs with alcohol further increases heat-related risks. Alcohol is a diuretic that promotes dehydration and also impairs the body's temperature regulation. Combining alcohol with opioids or stimulants during hot weather creates a particularly dangerous physiological stress.

Clinical Consequences: What Families Should Know

Understanding the medical realities of heat-related overdose can help families recognize emergencies and respond appropriately.

Signs of Heat-Related Overdose

The symptoms of a heat-related overdose may differ from a typical opioid overdose and can include:

• Classic overdose signs: Pale, clammy, or bluish skin; slow or irregular breathing; gasping or gurgling sounds; inability to wake
• Heat-related additions: Hot, dry skin (in stimulant-related cases) or profuse sweating followed by sudden cessation (in opioid-related cases); confusion or agitation; nausea and vomiting; muscle cramps or weakness

Why Naloxone May Not Be Enough

While naloxone remains essential for reversing opioid overdose, it does not address heat-related complications. A person may have their breathing restored by naloxone but still be in danger from heat stroke or severe dehydration. This is why calling 911 is critical — emergency medical services can provide IV fluids, cooling measures, and monitoring that naloxone alone cannot.

The "Parked Car" Danger

Using drugs in a parked car during hot weather is particularly dangerous. Vehicle interiors can reach lethal temperatures within minutes, even when outside temperatures are moderate. The enclosed space traps heat, and the impaired judgment caused by substance use may prevent someone from recognizing the danger until it's too late.

What You Can Do: Practical Harm Reduction

Whether you use drugs, know someone who does, or are a family member concerned about a loved one, there are concrete steps to reduce risk during hot weather.

For People Who Use Drugs

Use less or go slow. Start with a smaller amount than usual, especially if using in an unfamiliar environment or during a heat wave. The combination of heat and substances can amplify effects unpredictably.

Never use alone. The buddy system saves lives. If you must use alone, call the Never Use Alone hotline at 800-484-3731 — a trained operator will stay on the line with you and send help if you become unresponsive.

Avoid using in parked cars. Cars become death traps in heat. If you need privacy, find an air-conditioned indoor space instead.

Stay cool and hydrated. Drink water regularly, seek air conditioning when possible, and take breaks from direct sun. Call 211 if you need help finding a cooling center.

Carry naloxone and know how to use it. Multiple doses may be needed, especially with fentanyl and other potent opioids. Don't hesitate to administer it — naloxone cannot harm someone who isn't overdosing.

Test drugs for fentanyl. Fentanyl test strips are available through many syringe services programs and can help you make informed decisions about what you're using.

For Family Members and Friends

Check in regularly. During heat waves, check on friends and family members who use drugs more frequently than usual. A simple text or call can make a difference.

Know the signs of overdose. Learn to recognize both classic overdose symptoms and heat-related warning signs. Trust your instincts — if something seems wrong, call 911 immediately.

Keep naloxone accessible. If you have a loved one who uses drugs, keep naloxone in your home and know how to use it. Many states allow naloxone to be obtained without a prescription at pharmacies.

Support cooling efforts. Help your loved one access air conditioning, cooling centers, or other resources to stay safe during extreme heat.

For Communities

Share alerts widely. When public health departments issue overdose spike alerts, share them through social media, community groups, and personal networks. Information saves lives.

Support harm reduction services. Syringe services programs, overdose prevention centers, and mobile health units provide essential services during crisis periods. Advocate for their funding and expansion in your community.

Recognize the intersection of climate and health. As extreme weather becomes more common, communities need integrated approaches that address both environmental and public health challenges.

Where to Get Help

If you or someone you know needs support, resources are available:

Immediate Overdose Response:

• Call 911 immediately if you suspect an overdose
• Never Use Alone Hotline: 800-484-3731 — stay on the line with a trained operator

Naloxone and Harm Reduction Supplies:

• Public Health Madison & Dane County Syringe Services Program: 2705 E. Washington Ave. or 2300 S. Park St., Madison, WI
• Many pharmacies offer naloxone without prescription

Treatment and Recovery Resources:

• Behavioral Health Resource Center of Dane County: (608) 267-2244
• SAMHSA National Helpline: 1-800-662-HELP (4357) — free, confidential, 24/7 treatment referral
• FindTreatment.gov: Search for treatment providers by location and service type

Heat Relief:

• Call 211 to find cooling centers and heat relief resources in your area

Looking Ahead

The Dane County alert is part of a larger pattern. As climate change drives more frequent and intense heat waves, the intersection of extreme weather and substance use will become an increasingly important public health concern. Communities across the country will need to develop integrated responses that address both environmental and behavioral health challenges.

For families affected by addiction, understanding these risks is essential. The same harm reduction principles that apply year-round — using less, never using alone, carrying naloxone — become even more critical during extreme weather events.

If you have questions about supporting a loved one through addiction or navigating treatment options, the resources listed above can provide guidance. And if you use drugs, please take this alert seriously: the combination of heat and opioids is particularly dangerous, but there are steps you can take to protect yourself.

Stay safe, stay cool, and stay connected.

Dr. Rachel Bennett, MD, is a board-certified addiction medicine physician. This alert was medically reviewed on July 4, 2026.