I associate these sounds with the act of sheltering from these elements, which prevents all kinds of physical activities and encourages passive, calm ones. A tendency towards hibernation and hot chocolate by a fireplace, a calm and pleasant association. Even if I focus on the negative aspects -- getting caught out in the rain and being cold and wet, I generally bundle up and conserve my energy rather than start jogging... not positive, but still calm.

Sufficiently strong weather and uncontrolled fires could put you at risk, but the extremely vast majority of my experience with these sounds has been with the safe varieties -- I don't think I'd find it as calming otherwise.