Rain
Both wet, stormy and cold, dry weather are possible this month. Yearly rainfall averages for October can frequently be both well above and well below mean levels.
Be prepared for all possibilities. Do not rely on heavy autumn rains to take care of watering new plants, unless you live in an area with very predictable rain at this time of year.
If you do need to supplement rainfall and water new or transplanted trees, shrubs and perennials, then use stored rainwater or recycled grey water wherever possible.
If there are heavy rains forecast, make sure that you have supported, tied in and pruned (if appropriate) all herbaceous plants and climbers, and that any newly planted trees are well staked.
Sunshine
The day length is now noticeably shorter, and the angle of the sun more acute, with decreased intensity. These are limiting factors to plant growth, together with lower temperatures and gusty winds.
Temperature
Temperatures can vary in October. Although the weather can still be mild at time, gardeners should prepare for frost as well.
In cold areas, you should already have moved your tender plants into the house, or to a heated greenhouse.
In mild areas you may be able to overwinter things in the garden, but you should have fleece, together with straw, bracken, paper or some other packing material, on hand in order to cover the more tender plants.
A thick layer of mulch over the died-down crowns of tender herbaceous plants can also be effective in ensuring their return next spring.
Wind
Winds pick up as the autumn progresses, with gales being more likely. The winds will blow the autumn leaves off the trees, creating a lot of clearing up work in the garden and putting an end to displays of beautiful autumn colour.
Wind-chill can make the weather feel colder, and can scorch the leaves of plants such as acers, which are mainly grown for their beautiful leaf colours and forms. Increasing the shelter in your garden may help with this problem.