Hot water and bacteria
The bacteria wouldn't see any benefit from the warm water in the ~30-60 seconds you're washing your hands, neither would hot water "sterilize" your hands at temperatures you could tolerate. The reason you wash your hands with hot water is because the hot water+detergent soap mix is better for removing oil and dirt than cold water+detergent, which is supposedly where bacteria reside.

Interestingly, there was a study published saying that washing with hot water doesn't have much of an effect on bacterial load. Hot water for handwashing--where is the proof? (Laestadius and Dimberg, 2005). I'd be interested to look more into their methods but the paper is behind a paywall and I don't have access at home.

Also, this paper, Water temperature as a factor in handwashing efficacy by Michaels et al. is open and shows no evidence that hot water is any better than cold water for removal of microbes.


  [W]ater temperature exhibits no effect on transient or resident bacterial reduction during normal handwashing with bland soap.