In the absence of adequate analytical climatic data, vegetation limits compared with existing climatic data can be used to determine distinctive regional climates. Two hundred and two (202) phytoecological releves were selected on well-drained till, homogeneous in texture and thus statistically valid. Within this group, the territorial distribution of the principal vegetation species were studied in order to define macro-climatic zones. Nine hundred (900) reconnaissances écologiques were then identified by a dominant physionomic vegetation type (i.e. a name describing the structure and type of vegetation) after which the Jame Bay territory (400 000 km 2 surveyed) was divided into 19 Land Regions.