Mountain snowpacks are melting earlier due to climate change, impacting streamflow. Researchers developed a method using sunlight and daily streamflow patterns to track snowmelt effects on streamflow. They found that streamflow starts earlier in warmer areas and colder regions are more sensitive to climate change. For every 1°C of warming, snowmelt-driven streamflow occurs 11 days earlier. This method can help improve predictions of streamflow changes in the future.