Day of

An expression used in weather observatories to count the occurrence of certain notable meteors or events over the 24 hours making up the day. It is applied to fog, frost, precipitation (rain, snow, hail...) or storms, among others. For example, a "day of frost" is counted if between 0 and 24 h of the day in question the minimum temperature has been equal to or below 0°C. As for a "day of precipitation," only one in which the amount collected in the rain gauge reaches or exceeds one tenth of a liter per square meter (or equivalently 0.1 mm) is considered as such. Apart from that, the rainfall day accounts for the amount of precipitation fallen between 07:00 UTC of one day and 07:00 UTC of the following day. The "day of storm," lastly, is one in which at least one thunderclap is heard or lightning and flashes are observed, even if the storm does not leave precipitation at the observatory.