Water normally starts to freeze at 0 °C, which is 32 °F, under typical everyday conditions (pure water, normal air pressure).

Quick Scoop: When does water freeze?

The simple answer

  • Under standard conditions, liquid water freezes at 0 °C (32 °F).
  • This temperature is called the freezing point or the melting point of water.

Why it’s not always “exactly” 0 °C

In real life, water can behave a bit differently from the textbook number:

  • Impurities and minerals: Dissolved substances (like salt or minerals) lower the freezing point, so the water may freeze below 0 °C.
  • Pressure: Changes in pressure can shift the freezing temperature slightly, although everyday variations in air pressure don’t usually matter much.
  • Supercooling: Exceptionally pure, undisturbed water can stay liquid even below 0 °C; it may not form ice until it’s disturbed or a tiny particle provides a “starting point” for ice crystals.

Scientists call that “supercooled” water, and under extreme, very pure conditions, liquid water can remain unfrozen down to about −51 °F (around −46 °C) before ice finally forms.

A quick everyday example

  • A puddle or a shallow tray of water outside will usually start forming ice when the air temperature is at or below 0 °C (32 °F) for a little while.
  • If you add salt (like on winter roads), that same water won’t freeze until it’s colder than 0 °C.

So if you’re just looking for the everyday number to remember for “when does water freeze,” it’s 0 °C / 32 °F, with the twist that real-world conditions can shift that point a bit.

Information gathered from public forums or data available on the internet and portrayed here.