There's not a specific temperature at which you can see your breath -- it depends on how much moisture is already in the air. On more humid days, you'll be able to see your breath at a warmer temperature.
Adults often think of seeing our breath as proof of just how miserably cold it is outside. But there are other ways to think of it. Just hang out with kids who still think it's exciting to see their breath (remember?).
Or, take the opportunity to reflect on the way your breath is connected to all other beings on the planet. In The Lost Gospel of the Earth, Tom Hayden writes:
We are all breathing the same air our ancestors did, the same air as those with whom we think we share nothing in common. We breathe through nature. The air we breathe is generated and maintained by trillions of active organisms, from bacteria and termites to flowers and redwoods. I breathe in oxygen and breathe out carbon dioxide; the trees in my yard give oxygen to us and receive the carbon dioxide...We all breathe individually, but there is only one breathing process going on. When I look at photos of the thin cradle of atmosphere around the planet earth, I am seeing the breath of life.Look for your breath, indeed.