Normal boiling point of water

Water's boiling point at exactly 101.325 kPa is 99.974 °C, not 100 °C. The old centigrade scale was built to make it 100 by construction, but the 1954 redefinition anchored the scale to the triple point of water and absolute zero instead, and left the boiling point to fall wherever the physics put it. Better measurements then showed the gap: about 26 millikelvin.

In practice the boiling point moves far more with pressure than that. It drops roughly 1 °C per 285 m of altitude near sea level, so water boils near 93 °C in Denver and around 71 °C at Everest base camp — the reason pressure cookers exist and the reason a steam trap's discharge temperature tells you the line pressure. Dissolved salts raise it slightly through boiling point elevation.