What are the effects of humidity on forming ice.... if any?

Answer 1

Sort of an interesting question. I'd be interested in what prompted it. What I can say is the only time humidity is related to ice is when the temperature reaches the frost point and water vapor is deposited (called deposition) on surfaces - cars, windows, the grass, etc. The higher the humidity the greater will be the frost formed, if winds are not too strong. Now as far as humidity effect on water turning to ice such as a pond, I see no effect at all, if that is where you were going. But it is a factor in the formation of frost.

Answer 2

Not much as the moisture in the air [i.e. humidity] freezes and falls in the form of frozen precip. That's why a long frozen environment [northern, mountain, polar] is severely DRY and the WXman reports movement of cold dry air mass
from Canada etc. Also that is why the below freezing air is involved in a high
number of static discharge jumps -- which mean that's a BIG item for refueling safety of aircraft! YOU WILL SEE FROZEN "dew or atmospheric
moisture" on windows etc. when it was present prior to a freeze.