A large reservoir of saturation deficit air is known to exist over the northern Arabian Sea and the adjoining land regions during the peak of Indian summer monsoon (ISM). The strengthening of monsoon low-level jet (LLJ) in the northern parts of the Arabian Sea during the break phase of ISM helps in transporting this dry air toward northwestern India. Here, we show that, a weakening (strengthening) of the zonal flow over the northern Arabian Sea can reduce (enhance) the influx of the unsaturated air to the Northwest India and thereby enhance (reduce) precipitation there. The variability in the zonal flow over the northern Arabian Sea is a direct geostrophic response to the variability in the meridional pressure gradient over the Northwest India. The interannual variability in the mean sea level pressure over the region explains the inter-annual variability of ISM precipitation during July-August over northwestern India. The contribution of El Nino Southern Oscillation in the interannual variability of precipitation over this region is not significant. The study of rainfall is crucial as it has a significant impact on people's lives and plays a vital role in a country's economy. The Indian summer monsoon (ISM) is the primary source of rainfall for India, accounting for approximately 60%-80% of the annual precipitation. However, numerous studies have shown that predicting rainfall remains challenging. Therefore, it is essential to understand the factors that influence rainfall and how they affect its dynamics. Previous investigations have highlighted the importance of moisture deficit air advection, as it suppresses convection over continental India during summer monsoon break phases. In this study, we examine how the presence of dry air over the northern part of the Arabian Sea and adjacent Middle East desert region can affect the subseasonal and interannual variability in rainfall over northwestern India. Here, we report that an anomalous north-south dipole pattern in the mean sea level pressure explains the changes in the advection of dry air, which, in turn, controls the precipitation variability over northwestern India. The lower tropospheric transport of unsaturated air controls precipitation variability over Northwestern India A north-south dipole pattern in sea level pressure variability explains inter-annual fluctuations in the advection of unsaturated air A lead-lag relationship between moisture deficit air advection and rainfall indicates potential predictability of rainfall variability