Actually, the body sends more blood downstairs to keep it from freezing. that's why hot showers work better, they make it warm enough so that the blood can be used elsewhere.
And why yes, I am insane
Well this will certainly go down as the strangest conversation I've had this week.
It is true that the sac does draw increased blood flow to prevent sterility, it is however also true that the vascular tissue that makes up the majority of the scepter of lordly might will empty of blood and retract as far as it is able, the same is true of the scrotum itself but it's ability to retract is limited.
It is also true that increased circulation does not equal more total blood in any region. During cold weather the heart beats faster and blood cycles more quickly, both to the brain and to the scepter of lordly might. Cold is good for the mind, as long as you don't drop too far.
The second advantage of the cold shower over the hot shower is that it kills the desire to engage in procreation, which is in and of itself the primary cause of a muddled mind in this case, not the fact that one's scepter of lordly might is drawing blood away from the brain. (A ridiculous notion, the brain is the last thing to have its circulation cut or dropped.) The amount of blood drawn by the scepter of lordly might -even a large one- is a pittance compared to the total amount of blood available in the body, a severe nosebleed can draw a similar amount without causing decreased brain function.
Drag me into the sun when it's 110 degrees and I'll sweat like crazy, I'll be good for grunt work and heavy lifting but don't expect me to be able to do much more than that.
Give me winter weather (15 degrees) and I'll meet you with a t-shirt and a smile, the frigid shower just doesn't get that cold but it's enough to get me in a thinking mood.