I put the mouse in a plastic bag and leave it out for about an hour until it's soft and then I run it under hot water (still in the bag) for about 10 minutes. Then I test it on my wrist. And it's usually... Warm. Not HOT. I'm always worried that if I get it too hot the rodent might explode, cause I heard they can do that if it gets too hot. Well.. Not explode but like break open I guess