Its 35 here right now.The dew point is 24. It a lot higher in the summer, usually about 60.
Could it ever be 0, the dew point? Or 80?
Less it can much lower. Where I worked the instrument air was put through driers that lowered the dew point to -60 degrees F.
It seems to me, though, that it can’t be any higher than the current temperature. The dew point is the temperature at which the current concentration of water vapor in the atmosphere would correspond to a relative humidity of 100%. Lowering temperature raises the relative humidity if the absolute humidity is kept constant.
If this critical temperature is below the freezing point of water, it is properly called the frost point, since the result of reaching this temperature will be frost rather than dew.