When it comes to racing in bad weather in Philadelphia you’d be hard pressed to find anyone more qualified on the subject than Cecily Tynan. Not only is she a meteorologist, but she is also a runner herself. So you are safe to assume she knows what she is talking about on the topic of running in bad weather. (You can see what she said about the Broad Street Run earlier this year here).
Below she has written a lengthy post on how to handle the pending weather for the Philadelphia Marathon. Also, make sure you keep yourself updated on the weather as we continuously update it here.