Temperature window for bacterial growth. Above about 120F harmful bacteria commonly found in water won't proliferate, but will survive. As you get hotter from

Temperature window for bacterial growth. Above about 120F harmful bacteria commonly found in water won't proliferate, but will survive. As you get hotter from there, they're killed off increasingly rapidly. Above 135 or 140 or so they don't survive long. In cold water they won't die off but also won't multiply quickly. The dangerous range is in the middle.