I start fires and hot romances, what am I?

Step foot in me, you are six feet under. You may come to me when you hear whistles, sirens, and thunder.

Why was the guy who was hit in the head with the can of soda lucky?

An observer of event in the surrounding for which I boil without warning till the mercury rise or fall to whom I will call you

Twenty horses race at a steady pace, never breaking, never overtaking. Children laughing, children cheering. No losers here, everyone's winning.