Heatwaves pose significant risks to human activities, health, and safety. Accurate prediction of heatwaves is crucial and remains a key objective in the S2S project. Literatures may overestimate regional forecast skill due to focusing on strong cases and without accounting for false alarms. Using long-term datasets from four subseasonal forecast systems, we assess the forecast skill for heatwaves in the mid-high latitudes of the Northern Hemisphere. Our analysis reveals that heatwave frequency, intensity, and duration can be predicted up to 2 weeks in advance at a hemispheric scale. In particular, heatwaves in Europe are predictable up to 2 weeks ahead, with warm anomalies extending to 3 weeks. In contrast, heatwaves in East Asia and North America show limited forecast skills, with only a 1-week lead time for heatwaves and 2 weeks for warm anomalies. These regional disparities may arise from predictability associated with circulation complexities and varying model capabilities in capturing key predictability signals. Notably, longer and more intense heatwaves do not consistently correlate with higher forecast skill, which varies by region. Our findings provide valuable insights for model developers, emergency responders, and the public, offering a more nuanced understanding of heatwave forecast capabilities.