I normally highlight some seasonal dangers that new riders may not have considered before, so if you are a newbie commuter and this is your first autumn, read on:
1. Wet leaves are slippery
2. Wet leaves over white road paint or smooth metal are very slippery. Don't lean over hard on wet leaves.
3. Low sun. This time of year (maybe a few weeks to go), when we see the sun it can be very low, on an East-West axis at normal commuting times. If you are riding into the sun, drivers behind may not see you so well. If the sun is behind you, drivers in front, eg waiting at junctions, may not see you. No light or hi viz gear can compete with thermonuclear fusion. Consider a detour, a change in commuting time or just be extra vigilant.
4. Debris from trees. Branches can get tangled in wheels and chain so don't ride over them.