Climatic records - prorate data for date?

When the daily reports are created, can we make the entered climactic data for rainfall prorate for how far along in the month it is? That is, if we have 3.00" rain for the month … when giving compared to normal, can the actual figure be compared to 1/30 (or 1/31,1/28 ) of the monthly climactic figure entered (3.00) - so that 1.24" actual is compared to 1.00" prorated (for 10 days) yielding +.24"

Temperature would be much harder, though perhaps it could just “fudge” temps several degrees (a couple Celcius) up or down at beginnings and end of months depending on the month.