The Importance of the Sun, from Leo Jia
I believe the sun combined with a comfortable climate is key for happiness. People, and all organisms, are just more active in it. Places like Boston or New Jersey just don't have it. A former classmate couple who moved from Chicago to Silicon Valley told us their feelings during the initial days was always like "Oh, the weather is great today, let's go do something" until they found the weather is always great.