According some transmundanes, Friday the 13th's are considered to be one of the few days ArchDemons are let loose from hell to roam around our dimension seeking out hosts for possession. If a Friday the 13th also happens to fall on a full or close to full moon, then the joy riding demons preferably seek out individuals who suffer from lycanthropy, a.k.a werewolfism.
You can see how this might put a damper on a werewolf's night... All of a sudden instead of worrying about accidentally eating your neighbors dog, you leave your neighbors life-less copse with its limbs ripped off in the ruins of their 3-2 with detached garage, his virginal daughter a little worse for wear and a throbbing headache in the morning that may or may not be your angry condo association members, pounding on your front door, torches ablaze and rifles loaded with silver bullets.
Therefore, even though today's moon phase is only in its First Quarter, we strongly recommend that any werewolf stay indoors tonight. The good news is that unlike last year series of F13's, this year we only have 2. T.G.I.F