Why do we see what looks like steam coming off rivers in the morning.. even in the winter and its been below freezing for days...

Because the water is warmer than the air - or else the rivers would be frozen straight through to the bottom.

Thank you for your reply.. I was looking for a more detailed approach.. I am aware of the basics.

The warmer river water is evaporating into the air, the cold air is causing the vapor to condense into a mist. Does the same thing in the summer but the air temps aren't cold enough to cause condensation so the dampend air can't be seen.

So it's not steam... it's water vapor... thank you :)

Technically it is steam, steam is vaporized water. Most folks think of steam as boiling water, around 212 degrees depending on altitude. Due to the very different temps this is condensed steam. Ordinary steam is not viseable, must condense to be seen

On top of what all the other answers have said, water holds an enormous amount of energy, so it will be warmer than the temperature of what whatever it is outside if it's a lake and its been warmer outside for the past couple days then it'll be steamy.