Can you be more specific?
The Manual of the Planes does list environmental conditions and some denizens.
The usual Inner Planes are the Elemental planes. The main 4 are the Elemental planes of fire, water, air and earth. If you go further The para elemental planes are Ooze, Smoke, Magma and Ice.
I personally use Ethereal travel to the Inner Planes. Astral Travel to the Outer Planes.