Seeing breath on air

[Karen2005]

As I was walking home from work this evening (about 6pm) I noticed I could see my breath on the air. Although it had been raining really heavily and was a bit chilly, it wasn't that cold. I thought you could only see your breath when it was almost freezing. What's the maximum temperature that this happens at, or is it more to do with the amount of moisture in the air?

[gen2]

It depends mostly on the humidity of the air but the temperature comes into it as well.

Condensation will be observed when the temperature of a body of air is cooled below its dew-point - the point at which it is saturated and connot hold any more water as a vapour. The air from your lungs is close to body temperature and almost saturated with water vapour.

If the outside air is very cold (say near freezing) then it is almost certain that the breath will be cooled below its dew-point and you will see the condensation.

If the atmospheric air is very much warmer it can naturally hold much more water vapour but if it is at saturation point already (100% humidity), it cannot hold any more vapour and your breath will become visible as you describe.

[SteveD]

Cute photo:

http://www.neillosin.com/DisplayPhoto.aspx?id= 335

[Karen2005]

Thanks for your answer, gen2. And that is an amazing photo SteveD. Never seen anything like that before.