Important note on the term precipitation days in the diagram There is no general definition of the term 'precipitation days' yet.The amount of precipitation is usually expressed in units of liquid water depth (e.g., centimeters or inches) of the water that has fallen on a horizontal surface at a given point and over a specific time interval (e.g., last 6 hours).However, sometimes this amount of water is so small that weather stations correctly report precipitation, but simply cannot gauge it.For example, a typical source for such 'non-measurable' precipitation is very light drizzle, dew or rime and even sea spray.Fog is the most common reason for precipitation fewer than 0.1 mm.The diagram of Tours/St Symphorien shows every day of precipitation including days with non-measurable precipitation. Therefore the actual number of rain days appears to be slightly too big. |
