Records from the Institute of Meteorology and Water Management station in Jelenia Góra on the monthly precipitation totals of the years 1951–2000 were used to analyse the variability of summer (June–August) precipitation in that locality. The study was based on a moving sample consisting of 30-year subsets of the complete record. The critical values of monthly and seasonal precipitation totals at different probability levels were calculated from the gamma distribution. The parameters of that distribution were estimated by the maximum likelihood method. Linear regressions were fitted with the estimated critical values. It was found that the critical values of summer precipitation at 0.90, 0.95 and 0.99 probability display a downward tendency. The average totals of the summer season and August precipitation show a significant downward trend which corresponds with an increased probability of precipitation below the lower limit of the standard value.

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