Pour d'autre info http://www.meted.ucar.edu/norlat/snowdensi...om_mm_to_cm.pdf Conversion Tables Conversion tables based solely on surface temperature seem to be routinely used by meteorological observers to estimate snow measurements (when the water equivalent has been correctly measured but snow has been blown around by the wind), or water equivalent measurements (from the snow depth when snow did not enter the collector). The conversion table used by the NWS is shown below. Surface temperature Snow/water ratio 28-34 oF 10:1 20-27 oF 15:1 15-19 oF 20:1 10-14 oF 30:1 0-9 oF F 40:1 -20 to -1 oF 50:1 -40 to -21 oF 100:1 Table 21: Conversion table used by the NWS showing the relationship between surface temperatures and snow/water ratios. Source: DOC/NOAA/NWS (1996).