Skewness analyses of cumulative rainfall and mean temperature for December-January-February periods during which eastern Pacific SST anomalies were in the lowest (coldest) 17% of the period 1895-1997. Shaded climate divisions indicate areas that experienced a significant incidence of above or below median seasonal climate. Confidence levels for skewness can be found under the Above Median colorscale legend. Where climate divisions are annotated, significant skewness in the extreme 25% of seasonal values was found, with (n/m) indicating n seasons in the first 25%, m seasons in the fourth 25%.

      During La Niña DJF periods marked by moderate to strong (i.e., lowest sextile) cold SST anomalies,skewness analysis shows significant tendencies to first quartile precipitation over Texas and Oklahoma. A similar tendency to dryness can found in the in the October-November-December, November-December-January and January-February-March La Niña precipitation analyses. Conversely, a significant incidence of above median precipitation is found over eastern Montana and portions of the Dakotas. The temperature analysis indicates widespread tendencies to fourth quartile temperatures over Texas and Louisiana. The tendency to above median temperatures over Texas matches the tendency to dryness in the precipitation analysis, suggesting a high incidence of relatively warm and dry La Niña winter periods over that state. Over the Northern Plains, an opposite tendency to below median temperatures is evident, which is more apparent in the analysis of November-December-January temperature.