3.4.2. Daily Air Temperature on 12 July 2010 and 15 August 2015

On 12 July 2010, the course of daily air temperature was found to be similar at all measuring points. The lowest air temperature was observed at 2–3:30 UTC, while the highest temperature was found at 13–15 UTC (Figure 6a). During the day, the air temperature differences between the individual measuring points were lower than at night. In the hours before noon, the range of air temperature fluctuations was less than 2 ◦C (minimum 1.7 ◦C at 10:30 UTC), while in the night and early morning they exceeded 5 ◦C (maximum 5.2 ◦C at 1:00 UTC). On the aforementioned day the lowest daily amplitude of the air temperature was found at Słoneczna (10.6 ◦C), while the highest was at D ˛ebina (16.8 ◦C).

On 11 August 2015, the course of the daily air temperature was similar in all measuring points. The lowest air temperature was observed at 4–4:30 UTC, while the highest temperature was found at 13–15:30 UTC (Figure 6b). During the day, the air temperature differences between the individual measuring points were significantly lower than at night. The smallest differences (about 1.5 ◦C) occurred in the morning (6:30 UTC) and the afternoon (16:00 UTC), while the largest were in the evening and night hours with a maximum at 21:00 UTC (4.8 ◦C). On the day analysed, the lowest daily

amplitude of air temperature was observed at Słoneczna (12.5 ◦C), while the largest were in D ˛ebina and Collegium Geographicum (16.3 ◦C and 16.2 ◦C, respectively).

**Figure 6.** Daily course of air temperature in Pozna ´n on 12 July 2010 (**a**) and 11 August 2015 (**b**).
