Over 8 400 bottom-hole temperature (BHT) values from the Canadian part of the Williston Basin were analyzed and a temperature high was discovered in the Weyburn area of southeastern Saskatchewan. Geothermal gradients, thermal conductivities, and heat flow have been investigated for most of the Mesozoic-Cenozoic clastic unit as well as the Upper Paleozoic carbonate-evaporite unit. Regional heat flow variations with depth occur which are closely related to the hydrodynamics governed by the topography and geology. The blanketing effect of low-conductivity shaly formations may cause a temperature anomaly in the south where the thickest Phanerozoic cover exists. However, the Weyburn high can be explained only partially in this way. Hydrodynamics has also contributed to formation of the temperature anomaly there. The process of forming the anomaly by the blanketing effect and hydrodynamics also contributed to oil deposition. There is a correlation between Mississippian oil occurrences in the southeastern part of the basin and the location of the Weyburn temperature high.