How to Manage Overdose Risk During Heatwaves and Illness

When the temperature climbs above 24°C (75.2°F), something dangerous happens to people who use drugs - their risk of overdose goes up. It’s not just about being hot. It’s about how heat changes your body, how drugs interact with that change, and how little support exists when you need it most. This isn’t theoretical. In New York City, during heat advisories, emergency calls for overdoses spike by 22%. In places like the Pacific Northwest, where summers used to be mild, overdose deaths during heat domes have jumped over three times above normal. And it’s happening everywhere - from urban centers to rural towns that never expected this kind of crisis.

Why Heat Makes Overdoses More Likely

Heat doesn’t just make you sweaty. It rewires your body’s chemistry. When you’re dehydrated - even just 2% of your body weight in fluid loss - drugs in your bloodstream become more concentrated. That means a dose you’ve used safely before can suddenly become too much. Studies show this can increase drug concentration by 15-20%. For stimulants like cocaine or meth, your heart is already working harder. Heat adds another 10-25 beats per minute to your resting heart rate. Add a stimulant on top? That’s a 30-50% extra strain. Your heart can’t keep up. That’s how overdoses happen - not always from too much drug, but from too much stress on your body.

For opioids, heat is just as deadly. Your body normally compensates for opioid-induced breathing slowdown by taking deeper breaths. But heat reduces that compensation by 12-18%. That thin safety margin? It disappears. And if you’re also taking medications for mental health - like antipsychotics or antidepressants - heat can make them less effective or more toxic. About 70% of antipsychotics and 45% of antidepressants behave differently in high heat, according to research from the Colorado School of Public Health. If you’re managing depression or psychosis on top of substance use, this doubles your risk.

Who’s Most at Risk

This isn’t a problem that affects everyone equally. People experiencing homelessness are especially vulnerable. In the U.S., nearly 38% of people without stable housing also have a substance use disorder. They can’t escape the heat. Shelters often turn people away if they’re using drugs. Air-conditioned spaces? Rare. Cooling centers? Most don’t even know they should be open to people who use drugs.

And it’s not just homelessness. People on fixed incomes, those without reliable transportation, or those who can’t afford water or electrolyte drinks are at higher risk. A 2023 CDC review found that only 28% of U.S. city heat emergency plans even mention people who use drugs. That means most public safety efforts - water distribution, cooling vans, check-in calls - don’t reach the people who need them most.

What You Can Do: Practical Harm Reduction Steps

If you or someone you know uses drugs, here’s what actually works during a heatwave:

• Reduce your dose by 25-30% - Even if you’ve used the same amount for years, heat changes how your body processes drugs. Lowering your dose isn’t weakness - it’s survival.
• Drink water every 20 minutes - One cup (8 oz) of cool water (50-60°F) every 20 minutes. Not soda. Not energy drinks. Not alcohol. Water. This simple habit cut heat-related overdose calls by 17% in NYC outreach programs.
• Use electrolytes - Heat flushes out salts your body needs. Electrolyte packets (like those used for athletes) can help. Keep them in your bag. Ask harm reduction groups for them - they often give them out for free.
• Never use alone - If you’re using, have someone nearby who can call 911. If you’re worried about judgment, use a buddy system with someone who understands. Or use a drug checking service - many now offer remote support.
• Carry naloxone - It doesn’t reverse stimulant overdoses, but it can save a life if opioids are involved. Many community centers give it out for free. Learn how to use it. Practice with a training kit.
• Check your meds - If you take prescriptions for mental health, talk to your doctor before a heatwave. Some meds need dose adjustments in high heat. Don’t guess - ask.

What Communities Need to Do

Individual actions save lives, but systems need to change too. Cities that have succeeded - like Vancouver, Philadelphia, and Maricopa County - didn’t just hand out water. They built real partnerships.

Vancouver opened seven air-conditioned respite centers next to supervised injection sites during the 2021 heat dome. They offered food, water, showers, and medical support. Overdose deaths dropped by 34%. Philadelphia distributes over 2,500 cooling kits every summer - with electrolytes, misting towels, and overdose reversal info. Maricopa County trained volunteers to do wellness checks - 12,000 in one summer, leading to 287 overdose interventions.

These programs work because they don’t punish people for using drugs. They meet them where they are. But only 12 of 50 U.S. states have officially included substance use in their heat emergency plans. That’s changing. In 2023, the U.S. government allocated $50 million to fix this. By December 2025, every state health department must have a plan that includes overdose risk during heatwaves.

What’s Coming: Climate Change and the Future

By 2050, climate models predict 20-30 more days each year will exceed the 24°C threshold where overdose risk spikes. That’s not a future problem - it’s already here. Cities that used to have cool summers are now facing heat domes. People who thought they were safe are now at risk.

New research is showing even more complex effects. Heat may be changing the gut microbiome by 15-20%, which could alter how drugs are absorbed. That’s still being studied, but it means today’s advice might need updating soon. The WHO now recommends that treatment centers adjust buprenorphine doses during heat events - because at 30°C+, its effectiveness drops by 23%.

This isn’t just about saving lives during a heatwave. It’s about fixing the systems that leave people behind. Cooling centers that won’t let people in because they’re using drugs. Police who take away water bottles. Doctors who don’t ask about heat exposure. These aren’t minor oversights - they’re deadly gaps.

Where to Find Help

You’re not alone. Harm reduction groups across the country offer free support:

• Need water, electrolytes, or a place to cool down? Call your local public health department or search for harm reduction organizations in your area.
• Need naloxone? Many pharmacies give it out without a prescription. Some even deliver.
• Need to talk about drug use without judgment? Text or call a peer support line - many are available 24/7.

If you’re a service provider - a nurse, a social worker, a volunteer - ask your agency to include heat risk in their protocols. Use the CHILL’D-Out screening tool. Talk to people about hydration. Don’t assume they know. Don’t assume they’re safe.