Cold Weather Raises Heart Risk More Than Heat, Study Finds

After one of the coldest winters in recent memory, scientists looked at how temperature affects the heart. They found that cold months cause many more heart attacks, strokes, and artery problems than warm months.

Past studies have linked extreme weather to heart deaths, but most focused on other countries or small U.S. areas. This new research looks at a large part of the United States and gives the most detailed picture yet.

Two Decades of Data Show a Clear Pattern

Researchers examined monthly temperatures and heart‑related death rates from 2000 to 2020 in 819 U.S. locations, covering about 80% of adults over 25. They discovered that the safest temperature is around 23 °C (74 °F). When it gets hotter or colder, deaths rise.

The link looks like a lopsided "U" shape. Both very hot and very cold days increase risk, but the cold side is far steeper. The study estimates that cold weather adds about 40,000 extra heart deaths each year—roughly 6.3 % of all heart‑related deaths. Over 20 years, that equals about 800,000 lives. Hot weather adds only about 2,000 extra deaths per year, or 40,000 in total.

Why Cold Weather Stresses the Heart

When the body gets cold, blood vessels narrow and inflammation rises. These changes make heart attacks and strokes more likely. Older people and those with chronic illnesses are especially vulnerable.

“As conditions like diabetes, heart failure, and kidney disease become more common, more people will be at risk from extreme temperatures,” one researcher noted.

Preparing for Weather‑Related Health Risks

The findings suggest towns should pay close attention to cold weather dangers, not just heat. Climate plans need steps to protect people during very cold periods.

Hospitals and emergency teams can also use this information to expect more patients when temperatures drop.

“Public‑health officials must ready their systems for a surge in emergency calls and hospital deaths during cold spells,” the researcher added.

Study Limits and Future Work

The team used monthly, not daily, temperature data and looked at groups rather than individuals. Future research will match daily temperature changes to emergency calls for heart problems.

The study was published online in the American Journal of Preventive Cardiology and was presented at the American College of Cardiology’s annual meeting in New Orleans, March 2026.