To give you the classic cop-out, it depends. Most of the streams I fish, I spend the majority of the time on the rocks and not in the water. I avoid waders whenever possible ( generally late March to early November). HOWEVER, if you are in a larger stream where you plan to spend extended periods standing in the water (especially thigh high or more) you may want to consider waders to avoid gradual hypothermia. For those who are more acclimated to the mountain streams (i.e., no live nerve endings left) even this type wading can bd done wader-less. So, it depends.
His eye is on the sparrow and I know He watches me.