The study examines the impact of increasing forest fire sizes on postfire land surface warming in temperate and boreal forests of the Northern Hemisphere. Using satellite observations, the research finds that fire size amplifies decade-long summer postfire land surface warming per unit burnt area. This amplification is more pronounced in evergreen needleleaf forests (ENF) and deciduous needleleaf forests (DNF) compared to deciduous broadleaf forests (DBF) and mixed forests (MF). The study also reveals that the effects of fire size on postfire surface warming are modulated by forest type, with broaderleaf forests showing less warming due to their lower fire vulnerability. The findings suggest that climate-smart forestry should aim to mitigate the climate risks of large fires by increasing the share of broadleaf trees and avoiding active pyrophytes. The implications of these findings include potential changes in stand regeneration, permafrost degradation, and regional to global climate feedback loops. Given the projected increase in fire size in northern forests, the study emphasizes the need for appropriate mitigation strategies to manage the climate risks associated with large fires.The study examines the impact of increasing forest fire sizes on postfire land surface warming in temperate and boreal forests of the Northern Hemisphere. Using satellite observations, the research finds that fire size amplifies decade-long summer postfire land surface warming per unit burnt area. This amplification is more pronounced in evergreen needleleaf forests (ENF) and deciduous needleleaf forests (DNF) compared to deciduous broadleaf forests (DBF) and mixed forests (MF). The study also reveals that the effects of fire size on postfire surface warming are modulated by forest type, with broaderleaf forests showing less warming due to their lower fire vulnerability. The findings suggest that climate-smart forestry should aim to mitigate the climate risks of large fires by increasing the share of broadleaf trees and avoiding active pyrophytes. The implications of these findings include potential changes in stand regeneration, permafrost degradation, and regional to global climate feedback loops. Given the projected increase in fire size in northern forests, the study emphasizes the need for appropriate mitigation strategies to manage the climate risks associated with large fires.