The Sierra Barrier Jet contributes to up to 40% of cool-season precipitation in Northern California, with maxima observed from the coast north of San Francisco through the Central Valley and into the Mt. Shasta–Trinity Alps region. When SBJs coincide with Atmospheric Rivers, they can produce more than 30% of the seasonal precipitation, intensifying the risk of flooding and landslides in these areas. Stronger SBJs are associated with higher integrated water vapor transport (IVT) and more intense Atmospheric Rivers, which can lead to extreme weather events. Communities in the northern Central Valley and mountainous regions should remain vigilant during such events.