Average and Median Rainfall for Lower RGV Stations
La Niña and 30–Year Averages Shown

Average and Median Rainfall for Brownsville, Harlingen, and McAllen (All La Niñas)
The graphs below show the average (left side of page) for the most recent 30 year cycle (1971 to 2000, solid bars) and median (right side of page) for entire period of record rainfall, and for La Niña years only (since 1950, shaded bars). Medians show the middle value of the data, and can be used to evaluate the skewness of a sample. The majority of the data shown are skewed "to the right", meaning that the average rainfall is higher than the median rainfall, denoting a lower frequency of higher rains but that such rains contribute greatly to the average.

Accumulated rainfall totals for three month intervals are shown. For example, "OND" shows the average rainfall for October through December, "NDJ" shows the average rainfall from November through January, etc. Rainfall values inside each solid bar are for either the 1971 to 2000 period (averages) or for the station period of record (medians); accumulations inside each shaded bar of the chart are for La Niña years. Click on each graphic for a full size image.

Average Rainfall, Brownsville, For La Nina and 1971 to 2000 climate average cycle, three month intervals (click to enlarge) Median Rainfall, Brownsville, For La Nina and 1878 to 2009 period of record, three month intervals (click to enlarge)
Average Rainfall, Harlingen, For La Nina and 1971 to 2000 climate averaging cycle, three month intervals (click to enlarge) Median Rainfall, Harlingen, For La Nina and 1911 to 2009 period of record, three month intervals (click to enlarge)
Average Rainfall, McAllen, For La Nina and 1971 to 2000 climate averaging cycle, three month intervals (click to enlarge) Median Rainfall, McAllen, For La Nina and 1941 to 2000 period of record, three month intervals (click to enlarge)

Average and Median Rainfall for Brownsville, Harlingen, and McAllen (Strong La Niñas)
The graphs below are identical to those above, except for strong La Niña’s – those which have at least one three month mean index value of -1.6 or lower. Note the improved correlation to very low three month precipitation averages through early spring in all locations. The current forecast for the 2010/11 winter indicates a strong likelihood that the ENSO Index will indeed average less than -1.6; a strong La Niña.

Average Rainfall, Brownsville, For strong La Nina and 1971 to 2000 climate average cycle, three month intervals (click to enlarge) Median Rainfall, Brownsville, For strong La Nina and 1878 to 2009 period of record, three month intervals (click to enlarge)
Average Rainfall, Harlingen, For strong La Nina and 1971 to 2000 climate averaging cycle, three month intervals (click to enlarge) Median Rainfall, Harlingen, For strong La Nina and 1911 to 2009 period of record, three month intervals (click to enlarge)
Average Rainfall, McAllen, For strong La Nina and 1971 to 2000 climate averaging cycle, three month intervals (click to enlarge) Median Rainfall, McAllen, For strong La Nina and 1941 to 2000 period of record, three month intervals (click to enlarge)
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