For Celsius

0º - water becomes solid - it's cold

25º - water is refreshing - ideal temperature

50º - water is scalding - dangerous

100º - water is boiling - guaranteed serious injure territory from this point forward

And, since nobody seems to reach an agreement...

For Kelvin

0º - matter has ceased to move; collapse of matter and reality as we understand it - it's cold

273.15º - water is remains solid - still cold

298.15º - water is a fluid, drinkable, safe to enter - ideal temperature

323.15º - water is capable of delivering serious injuries upon contact - dangerous

373.15º - water is passing into vapour form at high rythm - avoid proximity and all contact from this point forward