Infrared signature data on a number of unique military targets have recently been acquired under a limited variety of environmental conditions. A method has been developed for extrapolating these signature data to other environmental conditions without resorting to heat transfer modeling. The only environmental factors considered are solar loading, sky radiation, wind speed and air temperature, and vehicle operational state. Coarse faceted geometric models of the targets are constructed from a very limited number of material types whose responses to environmental factors are determined from the data. Projections for an armoured target are compared with the predictions of two signature models which utilize more detailed and sophisticated approaches.