I've lived in Florissant's Boardwalk subdivision (we're actually unincorporated Florissant) for 3 years and crime is below average. We actually moved from Rockford, IL which has a MUCH higher crime rate than St. Louis County (and that includes a MUCH higher murder rate). Our subdivision is quiet and the neighbors all look out for one anothers homes. The biggest problem we have is our extremely old neighbors who are both racist and who hate kids so they make it difficult for all of the kids on our street to play outside. If neither of them lived in those homes then I would say our particular street is just about perfect. Everyone has children within the same age and grade of each other. They all get along very well and again we look out for one anothers homes.
I can tell you that home invasions and car break-ins are the biggest issue that seems to plague most of Florissant. I would highly recommend to anyone that you get an alarm system for your home and make sure that you get to know your neighbors and who frequents their homes.
In regards to the severe weather issue and no basement, where have you looked for homes? Before we bought our home we rented and we looked EVERYWHERE in unincorporated Florissant and did not find any homes that lacked a basement. Getting closer to Old Town Florissant however I am unsure of simply because we have to remain in unincorporated because we have a Pit Bull and they're banned from incorporated Florissant.