When looking at weather observations, it is important to realize that a single weather observation represents the conditions existing during one particular time at one specific location.
Most observations are routine.
Reported conditions may or may not be regional in scope. For instance, rainfall reported at KLAX is not necessarily the same as the amount received in the Los Angeles region. 21 Observation is for the 21st day of the month. Present weather is light snow. This is from an automated station.