Boreal wildfires impact surface climates with consequences for plant physiology, permafrost thaw, and carbon fluxes. Post-fire temperatures vary over decades due to successional changes in vegetation structure and composition. Yet, the underlying biophysical drivers remain uncertain. Here, we quantify surface climate changes following fire disturbances in the North American boreal forest and identify its dominant biophysical drivers. To do so, we analyse multi-year land-atmosphere energy exchange and satellite observations from across Canada and Alaska. We find post-fire daytime land surface temperatures to be substantially warmer for about five decades while winter temperatures are slightly cooler. Post-fire decadal changes are characterised by a decrease in leaf area index during the first decade, a sharp increase in snow cover period surface albedo, and a decrease in the efficiency of heat transfer for about 2-3 decades. Evaporative fraction increases in the first three decades before returning to lower values again. We find that warming is mainly explained by a decrease in the efficiency of heat transfer while cooling is additionally explained by increasing surface albedo. We estimate that current daytime surface temperatures of the boreal biome of Canada are 0.18 °C warmer in the summer and 0.04 °C cooler during the winter due to fire. For a scenario with a strong increase in burned area, we estimate doubled warming from fire until 2050. Our study highlights the potential for accelerated surface warming in the boreal biome with increasing wildfire activity and disentangles the biophysical drivers of fire-related surface climate impacts.