A day when the soul feels that institutions should be closed. Nature is calling for you to have a day off from work or school, but lacks the proper requisite precipitation to facilitate. May be used in both areas that expect snowfall or not, and is absolutely valid regardless of the season.
Franklin: "My family back home in Jersey just got 8 inches of snow, I'm taking a spiritual snow day."
Franklin's Boss: "I can respect that. See you in the AM."
or
Kelly: "I can't make it in today."
Jeff: "Why not?"
Kelly: "It's a spiritual snow day. They haven't plowed yet, and I can't make it in."
Jeff: "...We're in Flagstaff Arizona, what the heck are you talking about?"
Kelly: "Thanks for understanding, I'll see you tomorrow."