A method of calculating moving standard deviations to give an idea of long-periodic fluctuations in the interannual variability of summer temperature is described and discussed from a statistical point of view. The method was applied to summer temperature records from 15 stations in Sweden and changes in the variability at those stations are treated. In addition the actual variability during the period 1920–39 is determined and compared to the interdiurnal variability of the same period.
In the second part of this investigation are studied frequency fluctuations of different circulation patterns over southern Scandinavia based upon the catalogue of daily weather situations during the period 1881–1950 published by the German Weather Service of the U.S. Zone in 1952. These fluctuations are compared with changes in the summer-temperature and its variability in South Sweden during the same period. It is found that the recent rise of summer temperature has been connected with a definite decrease in frequency of north-meridional situations over Europe and with an increase of south and warm-meridional cases as well as zonal situations. High variability seems to be connected with meridional circulation, low variability with zonal circulation. In a special chapter the fluctuations in variability of the Stockholm summer temperature since 1756 are discussed.