You are right, temperature can affect the running of a roller coaster.
In no scientist but from what I remember from my GCSE science days, the cooler the temperature, the higher the friction between the wheels and track, thus making it slower and increasing the chance of a valley.
That's why a coaster gets faster as the day goes on, especially on a hot, dry day. As the train runs around the track, the wheels and track warm up creating less friction.
Of course the material of the coaster needs to be taken into account as different materials react to different weather conditions.
I think I'm right, but I do expect loefet to come along and condem my GSCE science to hell :lol: