Autumn Weather Conditions

Due to poor weather conditions, we are expecting exceptionally poor rail conditions across the South Western Railway network in the coming days. This is likely to have an impact on our train services and may cause delays and alterations to train services.

What is poor rail adhesion/poor rail head conditions?
Why does this cause delays?
Why are conditions expected to be worse than usual in the coming days?
What is being done to clear tracks and reduce delays?