Influenza virus transmission is influenced by ambient temperature and relative humidity (RH). Using guinea pigs as a model, researchers found that both cold and dry conditions enhance transmission. At 20°C, transmission efficiency was highest at low RH (20–35%) and blocked at high RH (80%). Cold temperatures (5°C) increased transmission compared to 20°C, while high temperatures (30°C) reduced it. Transmission at 5°C was more efficient, with 75–100% transmission at 35–50% RH, and 50% at 65–80% RH. This was attributed to prolonged viral shedding, which increased the amount of virus in the environment. However, innate immune responses in guinea pigs at 5°C were comparable to those at 20°C, suggesting that cold does not impair immunity. The study supports the role of weather conditions in influenza dynamics, explaining why winter is a peak season for influenza. Low RH and cold temperatures may favor virus spread by increasing viral stability and reducing mucociliary clearance. The findings suggest that maintaining warm temperatures and moderate RH could help control influenza transmission indoors. The study provides direct evidence linking weather conditions to influenza transmission, offering insights into the seasonal patterns of the virus.Influenza virus transmission is influenced by ambient temperature and relative humidity (RH). Using guinea pigs as a model, researchers found that both cold and dry conditions enhance transmission. At 20°C, transmission efficiency was highest at low RH (20–35%) and blocked at high RH (80%). Cold temperatures (5°C) increased transmission compared to 20°C, while high temperatures (30°C) reduced it. Transmission at 5°C was more efficient, with 75–100% transmission at 35–50% RH, and 50% at 65–80% RH. This was attributed to prolonged viral shedding, which increased the amount of virus in the environment. However, innate immune responses in guinea pigs at 5°C were comparable to those at 20°C, suggesting that cold does not impair immunity. The study supports the role of weather conditions in influenza dynamics, explaining why winter is a peak season for influenza. Low RH and cold temperatures may favor virus spread by increasing viral stability and reducing mucociliary clearance. The findings suggest that maintaining warm temperatures and moderate RH could help control influenza transmission indoors. The study provides direct evidence linking weather conditions to influenza transmission, offering insights into the seasonal patterns of the virus.