What persent of percepitation does it have to be to rain

Percent^ and the percentage is just the possibility of rain. So say 30%, that means there's a 30% chance of rain.

I thank you mean "what percent of humidity does it have to be to rain?" 100%
If there is a 30% change of precipitation. There is a 30% change it will rain.
Oops, It has to be at 100% humidity in the rain cloud, it could be anywhere from 0% to 100% on the ground, usall 90%+.

Actually, precipitation can be rain, snow, sleet or hail. Which percentage of that is rain, depends on your location. I expect that the there is more snow than rain at the poles and more rain than snow at the equator, right? ;-)

100P%

This makes no sense. If it's precipitating, then that means it IS raining.