Urbanization in different regions of the world followed different spatial models. The article presents some characteristic features of urbanization in the area of contemporary Poland, taking into account the driving factors, the climate and soils, as well as the resulting model of spatial evolution of the urban network; that is, contact-based diffusion. The article points out that the spread of towns between the thirteenth and eighteenth centuries—that is, from the beginning of urbanization on the contemporary territory of Poland to the end of the feudal period—strongly depended on such factors as air temperature and general natural conditions for the development of agriculture. The research was based on an analysis of more than 1,000 urban foundations, and information on the specific distribution of selected climate phenomena. The article also draws attention to historic climate changes as a factor stimulating the dynamics of urbanization in the analyzed territory. This article provides new information on the specific character of urbanization in the area of today’s Poland, and refers to the problem of environmentally determined diffusion of towns in a considerable area of Central Europe. It also fits into a broader discourse on the role of climatic factors in shaping urban colonization in areas characterized by different climates.