A person starts a story: "It was a dark and stormy night." An avid gamer starts a story: "It was a <die roll>...lightless and <die roll>...rainy night." An avid wargamer starts a story: "It was a dark (35% visibility) and stormy, 7/8 overcast night at 21:16. The wind was blowing from the southwest at 21 kilometers/hour. Occasional flashes of lightning provided a 20% visibility increase for the remainder of the combat round in which they occured, at GM's discretion. The terrain caused a -3 modifier to be applied to all movement rolls."
(From the "Rest" of RHF)