Low-magnitude seismic events (0 ≤ Mw ≤ 3.8) recorded in southern Norway during the period 2000–2019 were used to calculate the sudden co-seismic temperature increases using a simple stress-drop model. The maximum temperature increase associated with an Mw = 3.5 earthquake was ~122°C. Simultaneously, we added 13 historical earthquakes to our study data, which occurred between 1657 and 1989. Here, the maximum temperature rise was ~560°C for an Mw = 5.6 event. The temperature values were analysed to derive local thermo-mechanical effects, such as thermal fracturing, frictional drop and the possible formation of cataclasites and pseudotachylites. Using the Kanamori's equations, we estimated the thermal energy released by individual events and in 2D and 3D cumulative patterns. To identify possible correlations between frictional energy, seismicity distribution and regional geology, the results were spatially correlated with a lineament zone located along the southwestern coastline and a heat flux map. Areas with high thermal energy values seem to be spatially linked with zones that exhibit a high density of lineaments and high heat flux located along the whole of the southwestern Norwegian coast.