Is it safe to shower during a thunderstorm?

These days, it is safe to shower during a storm. Newer homes have plastic pvc pipes for the plumbing. Lightning is a static electricity discharge that tries to find the path of least resistance to ground. Plastic is not a conductor of electricity, thus, lightning would not travel through plastic pipes. Older homes may have copper or metal pipes for plumbing. This can cause a slight risk of people getting shocked during a storm as copper and metal are great conductors of electricity. Even with metal pipes, the chance of getting shocked is low.

How old is your house? Outlets typically have 3 wires/prongs (some only use 2). The 3rd wire is a "ground" wire. In theory, this wire should be able to absorb any excess electricity, dispersing it safely into the ground. In older construction, they used to ground this wire by attaching it to the (metal) water pipes, which had ample contact with the ground as the pipe went out to meet the water main that feeds it. A direct hit with lightning would overwhelm this ground wire and damage electrical equipment, but and indirect hit, just might send enough of a surge down the wire that some voltage goes out your ground wire. Water pipes these days typically are made from PVC, and the eletrical code does not allow them to ground the wires to the pipes anymore (there is a grounding bar in you breaker box - I'm not 100% sure how this is grounded - perhaps a rod in the ground, etc.?)

no its not because its vulnerable to lighting one of the worst things you can do during a thunderstorm is to run water or turn on electronics such as the TV computer etc. why because water attracts lighting

Yes- as long as there are no windows or electronic equipment nearby.

what are you showering outside in the rain?