A few days ago i came across a phenomenon that i've never seen before. I saw white mist/fog rise from a metal fence. To set the scene, it was a few days ago in the morning around 9 am, winter around -20 C, very slight snow (as in you can only notice if you pay attention to the ground and it sparkles). The fog itself wasn't that much but just noticeable enough to get my attention. This has been bothering me for a bit so i'd really appreciate if someone could help. The fog rose from the top of a metal sheet fence much like the following image and ask any questions that might help. Thank you.

If the sun were shining, it would result in water evaporating on the top of the sheet, which would quickly condense in the air.

Is it possible for frost on a metal fence to sublimate directly to water vapor from the sunlight heating the metal up?