People from very cold climates tend to underestimate the impact of mild cold on areas that are not accustomed to it. What I can say is that I lived in a very mild part of Southwest China. Winters were cold and rainy, but usually in the 40s and 50s. My coworkers was from Minnesota, and she said her winters in China was the coldest time in her life. I’m from Sacramento, CA, but I live in DC now and it has been an adjustment.
Equipment is one issue. Houses in warm climates are often poorly insulated, not winterized, and generally just not designed to hold heat. When you build a house in Southern California, you probably aren’t thinking about how you are going to heat those cathedral ceilings or installing double paned windows in the sunroom. As a result, even with the heat going, houses can get quite chilly and well below comfortable temperature. Indeed, it’s not unusual for a poorly insulated house to be colder than the outside air. And while 40 degrees may not be that crazy cold when you are out and about, it can be unbearably cold when you are sitting around watching TV- and you may not have slippers and throw blankets to keep warm. Additionally, warm climate dwellers often don’t budget for increased heating costs during the winter, so they keep the thermostat low trying to save energy, rather than thinking of heat as one of the normal costs of living.
Likewise, people in mild climates tend not to invest in winter clothing. It took me months after moving from California to DC to realize that a hat and gloves were not whimsical fashion accessories, but rather essential items that I needed to have on me if I wanted to be comfortable. Warm climate people don’t have down jackets, heavy wool coats, or even fleeces, and even if we had layering items we wouldn’t really know how to use them, and we would feel awkward and uncomfortable wearing them. Cold-weather dwellers don’t really notice the little things they do that keep them warm- things like buying thicker socks, or wearing more closed toed shoes. Even when we dress in warm clothes, we aren’t doing it right by really leveraging our materials and keeping our core warm. That Target coat may look warm because it is builky, but it’s probably not as warm as a good fleece.
FInally, life is just different. Warm weather bus stops are not shielded from the wind. Our restaurants and venues don’t have coat checks. Our high schools don’t have halls, and students change classes in the open. We have more open parking lots, and they may be further away from the destinations. Public spaces- things like high school cafeterias, churches, and office hallways- may not be heated.
In short, in very cold climates you spend a little time being very cold, but basically all indoor spaces are set up to be warm. In mild climates, you end up being a little cold all of the time, and that becomes very uncomfortable and unpleasant.