Moving house this week, and if I've not already damaged my piano by somehow getting it out the house, onto a lorry and a 200 mile journey, it is now sitting in a garage for 4 days in cold weather because OH and I cannot get it up the stairs into our new house and we are waiting on the piano movers to come round. Realistically, what's the worst that can happen to it, and what's likely to happen to it?

It's a kemble upright.

Heat will do more harm than cold, and extremes of humidity aren't good.

So long as the garage is dry - not leaking rain, or with standing water on the floor (or te be more accurate - the air in the garage is of normal humidity) then your piano should be fine. It will probably take a few days to re-adjust to normal room temperature when it is put in its new home, so you should wait a while before having it re-tuned, and maybe having the action regulated.

It will probably go very out of tune and there might even be a few sticking notes, but after a few weeks indoors it will settle down, sticking notes should ease, and you can get it tuned.