Abstract
The paper demonstrates a dependency between the annual average daily air temperature course (cycle) in Warsaw and the profile of annual solar activity linked to rotation (with a period of 25–31 days). Waves of cold (ΔT <0) or heat (ΔT ≥ 0) were defined as ΔT deviations of daily average temperature (T) using a regression sinusoid f (t) with a period of 365 days. Cold waves were found to generally occur at times of low daily average solar activity (relative to 60-year average), while hot waves tended to coincide with high Wolf numbers. The cycles of the variables were derived using the sinusoid regression method (Boryczka 1998). The maximum sinusoid regression of the annual air-temperature cycle T is delayed by nearly one month vis-à-vis the maximum declination of the Sun. The maximum of the regression sinusoid of daily average Wolf numbers (W) was delayed from the maximum declination by more than two months.