I think it’s important to point out as well that there is a mesiarble difference between between the permittivity of free space and air. But to your point the difference is quite small: e_r air is 1.0006 whereas e_r freespace is 1.

While temperature and pressure do have an effect on e_r air I don’t know enough to say that net movement of the particles in one direction would have a measurable effect. My instinct is no.