Drought is a natural regular feature of any regional climate, including the Central Southwest Gulf Coast Region. Drought is defined as a deficiency in normal precipitation over a protracted time period, but can be exacerbated by unusually high temperatures and winds, or unusually low levels of humidity.

Drought has a profound effect on people and the environment and although it is considered a natural disaster, the human demand for water magnifies its negative impacts. Drought can be very costly and destructive and the effects of drought are both direct (i.e. loss of crops) and indirect (higher food costs). In fact, the US spends more on drought mitigation every year than it does on any other natural disaster.

Large portions of the CSWGCIN region have undergone extreme to exceptional drought conditions over the past six months.  Several drought affected areas in central and western Texas have received only 10% of normal rainfall over the past couple months, with March 2011 producing the driest March on record. The map depicts the six month Standardized Precipitation Index (SPI) blend from the period of November 2010 through April 2011.  The SPI is created by comparing current precipitation trends against long-term trends for a given area.  The precipitation deficit or surplus (compared to the average) is then rated on an intensity scale.  Drought conditions occur when the SPI is continuously negative and reaches values of -1.0 or less.  The results show continuous and widespread drought over the state for the past six months. 

The length of a drought is very important because although short-term drought affects soil moisture on a time scale of weeks to months, other usable water resources such as groundwater, streamflow and reservoir storage can take months to years to exhibit drought effects.