Why does rainy weather make people feel depressed? Is it the low air pressure? Or does the weather really affect people's mood?

It is normal that people's mood will change with the weather. Generally speaking, people's mood will become relaxed in sunny weather. On the contrary, people are more likely to become sad on cloudy or rainy days. You will think of many things, perhaps because of the melancholy mood on rainy days, and then think of some sad past events.