Perms and hair color. You can color hair that has been permed, but try to use a semi-permanent or 'no-ammonia' color instead of a normal permanent color (which uses ammonia and 20 volume peroxide). Have your hair permed first.
Mowing grass works best when the grass is dry, as grass tends to bend over from the weight of the rain, making it difficult to get a straight cut. It also clumps inside your mower cavity and on your lawn, which can lead to dead grass underneath the clumps if not raked promptly.
A problem with the ground being wet is that the wheels of the mower can sink into the wet ground, forming ruts in the lawn. Mow grass only when it's dry. Mowing grass when it's wet usually produces a very uneven cut. The wet grass clippings can also clump leaving a mess on the lawn and underneath your mower. Much more difficult to mow. The rotor not only has to cut the grass, but move the water as well.