October is an excellent time to Bike the Katy Trail. Like Shifty says, early to mid October may be the best. Oct and April can be damp and cool but not always. As a regular local rider, it is my favorite time to be out there. I would suggest you check on the BikeKatyTrail website, lots of info there with helpful people on the comment forum. It is a beautiful trail, 225 miles, that nearly spans the width of Missouri in a mostly rural setting. I have spoken to several cross country tourers that say it is a nice break from having to ride in the usual traffic. October is also a good time to catch festivals across the state.