Understanding drought-related impacts is critical for monitoring and responding to drought. To manage drought, you have to monitor impacts, and understand vulnerabilities or the consequences of those impacts.
The USDA produces monthly maps and charts showing locations and percentages of drought-affected areas which produce corn, soybeans, hay, cattle, and winter wheat. <a href="http://www.usda.gov/oce/weather/Drought/AgInDrought.pdf" target="_blank"><strong>(Sample image; click for current.)</strong></a>