@sv. You offered bounty for Shiva Linga question. Siva Linga needs to be always cool. In Sri Rudram from Krishna Yajurveda, very first anavaka says "Namsate Rudra Manvyava Utota Ishave Namaha..." It prays to Rudra, his anger, his arrows, his hands which leave the arrow... Indirectly his anger is negative or bad karma of this world. As per law of karma, negative or bad karma has irritating consequences. So, we keep Shiva linga (shiva) always cool to reduce collective bad karma.
