Exposure to snow, cold weather, high winds, or rain may precipitate Angina Pectoris ("Heart Chest pain") and Coronary Occlusion ("Heart Attack") in individuals known to have coronary arterial disease. As a response to this situation the body loses heat more rapidly, and body temperature drops to a subnormal level risking hypothermia. In these individuals heart failure is the cause of death.
According to a study in the "Chinese Journal of Physiology 1996; 39(2): 111-6", in cold weather the blood has a greater tendency to clot in the circulatory system due to an increase of coagulation factors. This information correlates with the normal physiological response of blood components to cold as follows:
Of interest is a population study published in England at the J. Epidemial Community Health 1997 Dec, 51(6) 643-8. indicated that from years 1976-92 in individuals over 50 years of age, 20 to 30 days patterns of cold weather below 59° F (15° C) were followed "rapidly by heart attacks".
The American Heart Association recommendation is: "People who are outdoor in cold weather should avoid sudden exertion, like lifting a heavy snow shovel full of snow. Even walking through heavy, wet snow of snow drifts can strain a person's heart."