Pennsylvania Water Science Center



Drought Condition Monitoring

Drought Indicators

About the program

CONTACT FOR MORE INFORMATION

Dennis Risser
(dwrisser@usgs.gov)

 

Precipitation

Precipitation is monitored in terms of departures (surpluses or deficits) from 30-year normal monthly precipitation quantities. Precipitation data for each of the 67 counties is available from the National Weather Service.

Drought conditions result from precipitation deficits. However, a single-month precipitation deficit does not indicate a drought. Rather, droughts result from accumulations of precipitation deficits over periods of three or more months. The table below provides the percentages of cumulative deficits, for periods ranging from 3 to 12 months, which are indicative of the various drought stages in accordance with Pennsylvania's drought monitoring criteria.

Precipitation Drought Monitoring Criteria

Duration of Deficit Accumulation (months)
Drought Watch (deficit as % of normal precipitation)
Drought Warning (deficit as % of normal precipitation)
Drought Emergency (deficit as % of normal precipitation)
3
25.0
35.0
45.0
4
20.0
30.0
40.0
5
20.0
30.0
40.0
6
20.0
30.0
40.0
7
18.5
28.5
38.5
8
17.5
27.5
37.5
9
16.5
26.5
36.5
10
15.0
25.0
35.0
11
15.0
25.0
35.0
12
15.0
25.0
35.0


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