Explain how

You mean the way I did in the parts you quoted after writing this?

You're getting a false sense of security. Do you think -1C = dangerous and 1C = safe or something?

No? Did I write that? I know the freezing point of water, so I know when I have to be careful. That's not strictly at the freezing point of water, but it is around that.

Wtf? Explain how

You should try to write actual questions, because I'm not sure what you're confused about. Say I want to water around 80-90°C - I heat water to boiling and then wait a bit. What's so difficult?