Data through September 17, 2013. Data sources: U.S. Department of Agriculture; National Drought Mitigation Center; National Oceanic and Atmospheric Administration
The Four Corners states of Arizona, Utah, New Mexico, and Colorado observed the biggest improvements in drought conditions during the past 30 days in the western U.S. Monsoon moisture interacting with several slow moving tropical and upper level low pressure systems brought record rainfall to much of the Southwest, delivering much needed relief to short-term drought conditions across the region. Large parts of Utah and Colorado were upgraded from severe to moderate drought classifications, while most of the extreme drought was erased from Arizona and New Mexico (Figure 3). Dry conditions north and west of the Four Corners states, however, kept drought conditions firmly in place across much of California, Nevada, and southern Oregon and Idaho. Overall, some level of drought covers about 81 percent of the western U.S., a slight improvement from the 87 percent noted in mid-August. The area under extreme or exceptional drought also fell from 20 percent in mid-August to 8 percent in mid-September.
The U.S. Drought Monitor is released weekly (every Thursday) and represents data collected through the previous Tuesday. The inset (lower left) shows the western United States from the previous month’s map.
The U.S. Drought Monitor maps are based on expert assessment of variables including (but not limited to) the Palmer Drought Severity Index, soil moisture, streamflow, precipitation, and measures of vegetation stress, as well as reports of drought impacts. It is a joint effort of several agencies.