The sudden drop in temperature here has provided a conversation starter for countless citizens: "Wow, it's cold, isn't it?"
It's an interesting thing to say, when you think about it. It can be assumed that everyone already knows that its cold, so commenting on it doesn't communicate information as much as it communicates a desire to connect, if just in a small way.
It's a way of reaffirming that we're in the same boat, if only because we're under the same sky. It's probably some sort of rule that conversations start with common ground, and weather is about as common as it gets.