I dont think it matters much, I just noticed roots on a cutting I had sitting in a glass of water for a couple of weeks.

If I clone in rapid rooters or rockwool I usually put a heat mat under the  tray to create humidity. If I clone in my DIY cloner I dont know because I never checked it but the  pump runs 24/7 so I would guess its warm. I dont use a dome with cloner and my results with it are nearly 100%