Well this is cool, per the CDC:
Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap.
Why? Because hands could become recontaminated if placed in a basin of standing water that has been contaminated through previous use, clean running water should be used. However, washing with non-potable water when necessary may still improve health. The temperature of the water does not appear to affect microbe removal; however, warmer water may cause more skin irritation and is more environmentally costly.
Emphasis mine. I’ve always washed my hands with cold water simply out of pure laziness. Good to know it has some benefits.