AbstractAn earlier study on the properties of supercooled water and some solutes obtained by simple graphical extrapolation of data available in the literature, determined above the freezing point, led to the hypothesis that water could have a temperature of structural arrest at t0=−30 °C for H2O and −22 °C for D2O. From the present investigation of many more properties of a widely varied nature, this discovery is confirmed throughout. The method is compared with the classical logarithmic Arrhenius and van′t Hoff methods that predict t0 always to occur at 0 K, and with the more recently used power law dependence method. With the latter, extrapolated plots intersect the temperature axis at or near to a value of ts=−45 °C, that is, systematically more negative than t0. It is argued that this ts value, which is the so‐called singularity temperature, is likely to be an artefact. It is suggested that, instead of using modified van ’t Hoff or Arrhenius relationships to describe temperature dependences in the full temperature range, polynomials in (t−t0) should be used.