National Weather Service United States Department of Commerce

Western Fall Storm: Southwest Monsoon

A fall storm will bring widespread rains, gusty winds, and high elevation snow to the Northwest. Gusty winds ahead of the front will produce critical fire weather threats for portions of the Great Basin, northern Rockies, and Front Range. Locally heavy monsoon rains may produce flash flooding in the Southwest. Strong storms are possible in the Great Lakes into the Northeast. Read More >

 

  Drought Severity Classifications

 

Ranges

Category

Description

Possible Impacts

Palmer Drought Index

CPC Soil
Moisture Model
(Percentiles)

USGS Weekly Streamflow
(Percentiles)

Standardized Precipitation Index (SPI)

Objective Short and Long-term Drought Indicator Blends (Percentiles)

D0

Abnormally
Dry

Going into drought: short-term dryness slowing planting, growth of crops or pastures. Coming out of drought: some lingering water deficits;  pastures or crops not fully recovered

-1.0 to -1.9

21-30

21-30

-0.5 to -0.7

21-30

D1

Moderate Drought

Some damage to crops, pastures; streams, reservoirs, or wells low, some water shortages developing or imminent; voluntary water-use restrictions requested

-2.0 to -2.9

11-20

11-20

-0.8 to -1.2

11-20

D2

Severe
Drought

Crop or pasture losses likely;  water shortages common; water restrictions imposed

-3.0 to -3.9

6-10

6-10

-1.3 to -1.5

6-10

D3

Extreme Drought

Major crop/pasture losses;  widespread water shortages or restrictions

-4.0 to -4.9

3-5

3-5

-1.6 to -1.9

3-5

D4

Exceptional Drought

Exceptional and widespread crop/pasture losses; shortages of water in reservoirs, streams, and wells creating water emergencies

-5.0 or less

0-2

0-2

-2.0 or less

0-2