Cold air in and of itself isn't bad. I duct in cold outside air (down to -40C) and have never had an issue with corrosion. Even at 100% RH, extremely cold air has a miniscule amount of moisture in it and the RH will quickly drop as temperature rises. There's the same amount of actual water in a cubic meter of -20C air at 100%RH as there is in 0C air at 20%RH, so you won't see condensation just from the air. What can cause issues are
1. Drawing in water, in the form of snow/rain.
2. Things not running. Blowing moist air over a running miner isn't really an issue as the heat from the miner will prevent any moisture buildup. If the thing is not on (or worse, if it is on but not running or generating any substantial heat) it can have moisture buildup.
3. Running them inside a warm (possibly humidified) house. Combine this with #2 above, but if you keep your house at 20C/50%RH the dew point is ~10C. You won't get moisture buildup on a miner while it's working, but it can if the miner cools down below that temperature from cold outside air and then stops running. Running electronics below ambient is always a bit of a risk and needs to be planned around.