The aim of the paper was to describe statistically changes of air temperature in the
area around Szczecin over the years 1991–2000 and to apply for this purpose a time series of
harmonic analysis in the annual cycle. On the basis of the original data, mean values of air
temperature in Szczecin in individual months, standard errors and extreme values were shown.
The mean air temperature in the studied decade (10 years) amounted to 9.03oC. A high
significance of annual periodicity of the studied feature was proved. The mathematical model
of temperature changes in the function of a successive day of the year was estimated. Very
good matching of the harmonic curve to the real data (determination coefficient R2
= 0.993) was recorded.