Winter (December to March) precipitation is vital to the agriculture and water security of the Western Himalaya and is largely brought to the region by extratropical systems, known as western disturbances (WDs), which are embedded in the subtropical jet. In this study, using seventy years of data, it is shown that during positive phases of the North Atlantic Oscillation (NAO+), the subtropical jet is significantly more intense than during negative phases (NAO-). Accordingly, the NAO affects WD behaviour on 2-3 year and 12-16 year timescales: during NAO+ periods, WDs are on average 20% more common and 7% more intense than during NAO- periods. This results in 40% more moisture flux entering the region and impinging on the Western Himalaya and an average increase in winter precipitation of 45% in NAO+ compared to NAO-.