The distribution and abundance of plants and animals, particularly poikilothermic animals that have a body temperature that fluctuates with the temperature of the environment, are influenced by climate (Andrewartha and Birch 1954). Introduced pests generally proliferate in regions with a climate similar to or more suitable than that of the region of origin. The better adapted a potential biological control agent is to the climate of the region of introduction, the greater the chance that it will establish and become abundant (See Prioritising Weed Biological Control Agents). Matching the climate of the region of introduction with that of the region of origin allows the potential geographic range of an invading species to be predicted. Conversely, exploration for potential agents in the region of origin can be guided by matching the climate with that of the region of introduction.

Estimating potential geographic distributions without computers would be impractical. Computer modelling programs can be used as tools in predicting the spread of a weed as a basis for economic evaluation of impact of the weed (See Benefit Cost Analysis). One such program is the CLIMEX model. While CLIMEX cannot estimate the impact that a  biological control agent will have on a weed species, it can help to identify those agents which have a similar potential distribution to the target weed. Agents whose potential distribution matches poorly with the distribution of the weed can then be given lower priority in the biological control investigation, saving time and resources.