The combination of cold weather and high levels of humidity can be fatal for those with heart problems, according to a group of Greek scientists whose groundbreaking research showed that a third more fatal heart attacks occur in the winter than in summer.

A group of cardiologists from Athens’s Ippocrateio Hospital studied statistics related to fatal heart attacks recorded in 2001 alongside daily reports by the National Meteorological Service (EMY) regarding temperature and humidity levels.

The research revealed that the average number of fatal heart attacks per day recorded in the winter of that year was about 32 percent greater than the daily average that summer. For those aged over 70, the number of fatal heart attacks recorded in December was double that in June.

In December, the average lowest temperature was 5.9 degrees Celsius (42.6 Fahrenheit) with 72.6 percent humidity as compared to 34.3 degrees Celsius (93.7 Fahrenheit) and 43.6 percent humidity in August.