The article deals with correlation analysis of district heating (DH) processes using temperature contour (TC) approach based on investigation of the functional dependence between outdoor temperature, Tout, as the regressor, and DH process characterizing thermal or hydraulic parameters, PDH, as the regresent, e.g., supply and return water temperature, TS&TR, as well as water mass flow, V. The time series of outdoor temperature, {Tout'i}, and supply water temperature, {TS'i}, as well as Tout&TS-scatter plots of (Tout'i; TS'i)-point data set have been examined more in details. It has been shown that using TC-approach one can additively construct linear regression models corresponding separately to each TC, and thereafter combining these models together and creating full regression curve for whole Tout&TS-scatter plot. Also frequency distribution functions (FDF), dFr(Tout)&cFr(Tout) and dFr(TS)&cFr(TS), have been calculated for different size TC in order to explore corresponding (Tout'i; TS'i)-point data set immanent data structure. In the case of asymmetric TC it has been stated that (Tout'i; TS'i)-points most likely are uniformly distributed along TC base-interval. However, along TC contiguous-interval (Tout'i; TS'i)-points most likely are normally distributed.