You are not going to get high from getting THC into you skin pores. If this were possible, you could get high by simply picking weed or rolling the weed in your fingers.

The steam from the hot water will open additional capillary capacity in the bronchial tubes leading to the lungs. Thus, you are simply able to absorb more THC because of the expanded surface area.

Steam or water vapor, will actually trap smoke particles from the air and drop down or stick to the walls and you skin.

However, since your immune system has no circulatory pumps, getting THC inside the skin via the pores would have no way to be transported to the brain anyhow.

Besides, if you gotta shower to get high, get better weed.