The special interest in weather is not for the sake of inerest only but for knowing the weather so that they can plan their daily activites better.
In winter time, without knowing the weather condition, they might be stranded in a storm for an outing with their loved ones. In summer, if they go campimg, the stormy weather will destroy all the fun they have anticipated.
I have a perfect example for this matter. David, a friend of mine, went skiing with his girl friend. Without checking the weather, they ended up in a hotel for the imclement weather for the whole time they were supposed to skii.
In a word, the interest in weather, or the greetings with weather, either one of them starts with a practical reason,