Abstract
Heat and cold waves in Warsaw (the Okęcie district) have been determined determined basing on daily average air temperature values in Warsaw (the Okęcie district), measured for 60 years between 1951 and 2010. Air temperature cycles, i.e. periods, amplitudes and phases have been determined by means of a sinusoidal regression method. Especially worth noting are 15 to 18-day long cycles of air temperature in given months (e.g. 16-day long cycles during 6 months: March, April, May, August, September, and October). Heat and cold waves result from interferences of cycles whose duration ranges from several to teen days of daily temperature values, and long-term cycles of average annual temperature.