I have been advising people not to wet the head and hair first when showering as this is in the wrong sequence.
This will cause the body to adjust its temperature too quickly because we are warm blooded. By performing this incorrect sequence, blood rushing up the head may cause capillary or artery breakage hence a stroke and a fall.
Right way of showering is to start wetting the body from the feet up to the shoulders slowly.
A sensation of vapour coming out of the crown on the head or bristling of body hair may be felt for some people.
Follow this procedure then shower as usual.
Especially useful for people with high blood, high cholesterol and even migraine.

This may make sense. I'll have to dig more into it

this writeup is not far from the truth.