Here we show that there is a significant relationship between Nino 3.4 ENSO anomaly (Dec--Jan average) and precipitation in the southwestern United States. This contributes to increased frequency of dust events in the years following strong La Ni¿a and El Ni¿o years. High probabilities (60%--100%) exist for an elevated frequency of dust events in years when the ENSO anomaly, annual precipitation, or annual P/PE falls below the 10th percentile. This analysis provides a quantitative framework in which to evaluate the expected effects of climate change on this and other arid regions.