Actually, most Canadians live near the border of the United States in a temperate area, which has some elements of each extreme. The hot summer is a very yang force, meaning that it is hot and light, and things move quickly. This is a time when we seek balance by yin substances that are very cooling and add more water to our bodies. The winter is a very yin force, being colder, darker, and more slowing. For balance we eat things that are more warming and substantive.
Heat moves things and coolness slows things down.
So, one reason we should eat hot things is seasonality. People can be hot or more yang in quality, or more cold and yin in quality. A person who is very yang in quality, hot, active and perhaps very angry, should probably be careful to try to take in food that controls this and avoid meats, cheeses, and herbs like ginseng. However, a person who is usually cold and tired and perhaps depressed would only make themselves worse by eating food that is either cold or raw. The number of people we see in today's society are by far more yin in nature.