Japanese are always whining/commenting on the weather. It's mostly just their way of acknowledging each others existence, but as American's it comes of as really whiney. When you walk down the street, anyone who you make eye contact with will comment on the weather. The polite way to start most conversations is to start with the weather. If it's hot out they say atsui desu ne - it's hot huh. If it's cold they say samui desu ne - it's cold huh. The normal polite thing to either is hai, soo desu - yes it is. Because I have found that I make the best impression on people when I am myself, even when being myself breaks some cultural rules I usually respond with mmm, skii desu - mmhmm, I like it. Most people get a kick out of it, and even when it's so hot that I feel like I'm melting, I feel a little better about the weather because I convinced myself with my own lie.
Japanese frequently ask me how Americans talk about the weather. My short answer is usually that we don't. For those that are more interested in the cultural difference, I tell them that unless the weather is really impressive, ie high winds, pouring cats and dogs, or we're having a blizzard we try not to talk about the weather. We don't talk about the weather otherwise at work, because it reminds us how much we would rather be outside, but if you are outside with someone else, we usually like to say it's nice today.
The idea of just wanting to be outside for the sake of being outside, doesn't really work in Japan. Japanese people use the phrase it's too sunny un-ironically. Because Japanese have a near phobia of the sun, and go to great lengths to prevent sun damage. Most Japanese people spend as little time outside as possible in the summer.