National Drought Mitigation Center Drought Monitor

Displays a map of current drought conditions over the entire United States. Drought areas are classified by their intensity, with D1 being the least intense and D4 being the most intense. D0, or drought "watch areas", are either drying out and possibly heading for drought, or are recovering from drought but not yet back to normal.

time period: current; updates weekly.

source:
http://droughtmonitor.unl.edu/data/kmz/usdm_current.kmz

info:
http://droughtmonitor.unl.edu
http://drought.unl.edu