What is the maximum Clear Sky Light Pollution rating to see the 2018 Perseid Meteor Shower?
The darker the better.

There are meteors of different brightnesses in the Perseid shower, including some fireballs that can be seen in any (cloudless) sky.

But many of the meteors are dimmer, and the quoted rate of 60 per hour assumes dark skies.  As there is no moon tonight, you would benefit if you can get to a dark sky location.  If you can see the milky way, you can see the Perseids.

I am under a blanket of cloud, but have seen a few while out running on Wednesday.