The reference evapotranspiration (ETo) is a climatic variable that tries to represent the evaporative demand of the atmosphere in a definite area. As well as precipitation (P), ETo is an important variable to consider within the climatic characteristics of a region, and one of the essential components of the hydrological cycle. The need of ETo and P values on sites where there are not meteorological stations, makes necessary the use of spatial interpolation techniques. Based on data supplied by a network of an automatic and standardised meteorological stations, located in the Spanish region of Castilla‑La Mancha, ETo is calculated using the Blaney‑Criddle USDA‑FAO method. Regional maps are drawn using the probabilistic technique of spatial interpolation known as Theory of the Regionalised Variables or Geostatistics. Values of ETo and P were available at the 164 locations. The spatial variation of both variables are satisfactory described: monthly and annual, by spherical semivariograms. The maps obtained by kriging are in agreement with the general climatic characteristics of the zone. They also permit identifying susceptible zones of individual management during the irrigation season.