Cold weather is hazardous to those of less robust health, especially the elderly and those in physically weakened condition. This hazard is considerably exacerbated by inadequate heating or shelter, as in the case of the homeless. Even when preparations are made, cold spells typically effect transportation, notably across mountain passes. This can affect distribution of food where supplies are inadequate.
Increasingly, as a result of the greenhouse effect, winds often carry a lot of moisture with them, evaporated from the surface of overheated tropical oceans. When this moisture is carried in clouds to higher latitudes it precipitates out, as increasing rain during the spring and autumn and as more snow and ice during winter. Thus winters get longer and colder.
Winters have been getting longer and colder for the past 50 to 100 years. During the past 15 years, Northern hemisphere winters have been the coldest in recorded history with record snow falling late in the season in many areas. In the last 40 years, longer winters have reduced the growing season by almost one month in the midwest of the USA.
In 1987 a severe cold wave swept across Europe paralyzing transportation, closing schools, businesses and governmental offices, causing more than 264 deaths, raising oil prices and causing a large number of accidents. In 1993 concerns were expressed that winter would place 4.25 million lives at risk in war-torn Yugoslavia, including 2.8 million in Bosnia. A similar situation had been averted the previous winter by massive inflows of humanitarian aid. Also in 1993, a cold spell raised concern in France about the condition of an estimated 10,000 homeless. In 1994 it was estimated that winter cold claimed 50,000 lives each year in the UK, of which over half resulted from heart attacks and strokes due to the tendency of blood to become more concentrated with cold and thus to clot more readily. In the USA the 1994 winter was expected to cost the insurance industry some US$1 billion for damage caused by storms.