3.4.1. Tmax in the Cold Waves

The cold wave in the entire area of the city began on 7 and lasted until 11 February (Figure 5a). The average Tmax during the wave ranged from −4.3 ◦C in Collegium Geographicum to −3.3 ◦C in Collegium Minus and −3.5 ◦C in Piekary. In most of measurement points, the lowest Tmax was recorded on 9 February. It varied from −5.2 ◦C in Collegium Geographicum and Słoneczna to −3.3 ◦C in Collegium Minus.

The beginning and ending of the second analyzed cold wave was variable over the area of the city. It began the earliest in Collegium Geographicum and in Rusa and Słonecznej—on 14 February, one day later in Ławica, Strzeszyn, and Swierczew, and on the subsequent day in D ˛ ´ ebina (Figure 5b). In Collegium Minus and Piekary, the beginning of the wave was recorded only on 19 February. The discussed cold wave ended on 26 February, and one day earlier in Collegium Minus. The lowest Tmax over the entire area of the city was recorded on 22 February. It varied from −9.4 ◦C in Ławica to −6.7 ◦C in Collegium Minus.

**Figure 5.** Tmax during the cold wave of 7–11 February 2010 (**a**) and 14–26 February 2011 (**b**).
