Each column shows
the average amount of rain which fell on a rainday in the previous twelve
months. A rainday is a day on which more than 0.5mm fell in the 24 hour period
09.00am to 09.00am. The monthly value is calculated by dividing the monthly
amount of rainfall by the number of raindays in the month and the twelve month
running average is calculated by averaging these monthly values.
The last column
(extreme right) shows that between March 2006 through February 2007 the average
amount of rain to fall on a rainday was 4.7mms.