*3.3. Tmax, Hot Days and Heat Waves in the City Area in 2008–2015*

In 2008–2015, the average Tmax in the city area was 23.8 ◦C and changed from 22.3 ◦C in Collegium Geographicum to 25.1 ◦C in Piekary. At all points, the coldest season was recorded in 2009. The average Tmax then changed from 21.6 ◦C in the Collegium Geographicum to 24.3 ◦C in Piekary (Figure 4). Also, at the two points (Collegium Geographicum and Słoneczna), the same average Tmax as in the summer of 2009 was recorded in the 2014 season. On the other hand, at most points, the highest mean Tmax in the summer occurred in 2015 and ranged from 21.9 ◦C at the Collegium Geographicum up to 25.8 ◦C in Strzeszyn and Piekary.

**Figure 4.** Average Tmax in the summer season and the number of hot days in 2008–2015 in the city area.

In the studied years, the total number of hot days in the city ranged from 131 days at Słoneczna to 197 days in Collegium Minus and Piekary. Apart from two points (D ˛ebina and Piekary), the least hot days were recorded in the coldest season (summer 2009) and their number ranged from 11 days at Słoneczna to 25 days in Collegium Minus and Piekary (Figure 4). In turn, the hottest days occurred in 2015, and their number changed from 29 days at Słoneczna to 35 days in Collegium Minus, D ˛ebina and Ławica.

A total of 10 heat waves were recorded in the city, of which five heat waves occurred at every measuring point. These were the waves from 2010 (8–17 July), 2014 (4–9 July, 15–23 July, 26–30 July and 2015 (2–18 August). The start and end dates of these waves (except for the wave from 2015) were similar throughout the entire city. In turn, three heat waves occurred in the city area, but they were not recorded in the Pozna ´n–Ławica station. These were the waves of 2008 (30 May–3 June), 2009 (29 June–4 July) and 2011 (3–8 June). Across the city, the longest heat wave was recorded in August 2015. The length of this wave ranged from 10 days (6–15 August) at Słoneczna to 17 days (2–18 August) in D ˛ebina and Collegium Minus.
