Make Patrick, the paper chain scarecrow and hang from the ceiling to review patterning, counting, subtraction etc. Make enough links in an ABAB or ABC color pattern, for however many days are in October. Tear off a link as each day passes.
Via discussion, have students count how many days are left 'til your Halloween party, field trip to the pumpkin patch or whatever. A raffia bow adds that finishing touch. If you have time, have students make their own scarecrow in a variety of colors. Suspend from the ceiling or along a hallway wall for a lovely autumn display.
If you're tossing in some scarecrows into your November activities to add a bit of variety to turkeys, children can add 6 links to Patrick, and write 6 things that they are thankful for.