What is the lowest temperature water can achieve without freezing and how does this effect its viscosity?

Answer 1

Normally at 0ºC or 32ºF. At that point water just begins to crystalize.

There are cases when water will not freeze, like
- freezing point depression due to hydration,
- freezing point depression due to osmotic effects (these are both equilibrium effects),
- supercooling: the delay or absence of formation of an ice crystal in the absence of efficient ice nucleators and/or
- the high viscosity

For every 0.5ºC (1ºF), water's viscosity will change by about 1.5%.

Water viscosity is inversely related to temperature. The lower temperature, the higher viscosity.

But, water's dynamic viscosity at 0ºC is 3.732µ [ 10-5 (lb.s/ft2)] and the kinematic viscosity is 1.924v [10-5 (ft2/s)].

Answer 2

You can cool water down to minus 40 (It's the same in both fahrenheit and celsius) before it freezes provided there are no dust particles to act as nuclei for freezing to start.