And: If there is written "P0003", does it mean that the precipitation is 3 inches, or 0,03 inches of rain?

Question

and does it mean, that this amount is right now, or during a certain period of time?

Answer 1

Hourly Precipitation Amount (Prrrr).  At designated automated stations, the hourly precipitation amount shall be coded in the format, Prrrr, where P is the group indicator

and rrrr is the water equivalent of all precipitation that has occurred since the last METAR. The amount shall be coded in hundredths of an inch. For example, "P0009" would indicate 9/100 of an inch of precipitation fell in the past hour; "P0000" would indicate that less than 1/100 of an inch of precipitation fell in the past hour.



The group shall be omitted if no precipitation occurred since the last METAR.

http://www.ofcm.gov/fmh-1/pdf/L-CH12.pdf