Fall severe outbreaks do occur, typically produce by strong dynamics in association with the storm system that accompanying the squall of wind and rain. Supercell storms or derechos are not apt to occur in October but severe weather can occur thanks to the dynamics of gusty winds associated with stronger storm systems.
A strong Fall storm in Canada dragged a cold front through our region, providing a soaking dose of wind and rain throughout the Delaware Valley that started during the morning hours and continued into the late afternoon. Philadelphia picked up 1.35" of rain, which isn't a substantial amount historically, but it was a soaking that was punctuated by a gusty squall line that swept through during the afternoon hours.
That line, which moved through between 3 and 4:30 PM, produced at least one tornado in the region. The one confirmed twister killed one individual in Hainesport, Burlington County when a tree limb fell and struck that individual. Damage was far more prevalent in New Jersey, which had snuck into the warm sector ahead of the line of storms.
Fall 2003 was an active severe weather season overall -- with Hurricane Isabel and three other severe weather events that followed in the weeks after Isabel moved through. The NWS has a pretty good writeup on the events that occurred ten years ago, with a good description of the dynamics and the background that lead to each of the events (post-Isabel) occurring. With the Midwest severe events from last Thursday night and Friday, it shows that even as we work into the cold season that dynamics will trump diminishing heat and daylight to produce severe weather events.