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.
the main reason people don't mow when its wet is that the grass clumps up, it doesn't bag very well and it ends up being a mess, you will end up with clumps of wet grass left on your lawn which will create dead spots because the cut grass will block the light to the live grass underneath.