Absolute humidity (AH) significantly influences influenza virus survival (IVS) and transmission (IVT), more so than relative humidity (RH). Studies show that AH explains 50% of IVT variability and 90% of IVS variability, compared to 12% and 36% for RH. In temperate regions, both outdoor and indoor AH exhibit a strong seasonal cycle, with low levels in winter, aligning with increased IVS and IVT. This seasonal pattern supports the hypothesis that AH drives influenza seasonality. A laboratory study on guinea pigs found that lower RH increases IVT, possibly due to more efficient production of virus-laden droplet nuclei and longer airborne survival of virus. However, analysis of data revealed that vapor pressure (VP), derived from AH, had a stronger effect on IVT than RH or temperature. VP is calculated from temperature and RH and is a measure of AH. Further analysis of IVS showed that VP strongly influences IVS, with lower VP leading to higher IVS. This suggests that VP modulates IVS, which in turn affects IVT. The study also found that lower RH and VP increase droplet nucleus production, which may contribute to airborne transmission. The findings indicate that AH is a more significant factor than RH in controlling IVS and IVT. Humidifying indoor air could reduce influenza transmission, especially in high-risk areas. However, the exact mechanisms through which AH affects IVS are not fully understood. Future studies are needed to explore the effects of AH on other transmission modes and to validate the findings through additional experiments and models. The study also highlights the importance of AH in global influenza seasonality and its potential impact on future influenza outbreaks in a warming world.Absolute humidity (AH) significantly influences influenza virus survival (IVS) and transmission (IVT), more so than relative humidity (RH). Studies show that AH explains 50% of IVT variability and 90% of IVS variability, compared to 12% and 36% for RH. In temperate regions, both outdoor and indoor AH exhibit a strong seasonal cycle, with low levels in winter, aligning with increased IVS and IVT. This seasonal pattern supports the hypothesis that AH drives influenza seasonality. A laboratory study on guinea pigs found that lower RH increases IVT, possibly due to more efficient production of virus-laden droplet nuclei and longer airborne survival of virus. However, analysis of data revealed that vapor pressure (VP), derived from AH, had a stronger effect on IVT than RH or temperature. VP is calculated from temperature and RH and is a measure of AH. Further analysis of IVS showed that VP strongly influences IVS, with lower VP leading to higher IVS. This suggests that VP modulates IVS, which in turn affects IVT. The study also found that lower RH and VP increase droplet nucleus production, which may contribute to airborne transmission. The findings indicate that AH is a more significant factor than RH in controlling IVS and IVT. Humidifying indoor air could reduce influenza transmission, especially in high-risk areas. However, the exact mechanisms through which AH affects IVS are not fully understood. Future studies are needed to explore the effects of AH on other transmission modes and to validate the findings through additional experiments and models. The study also highlights the importance of AH in global influenza seasonality and its potential impact on future influenza outbreaks in a warming world.