## 2 Materials and Methods
### External Conditions During the Monitoring
#### 2.2.2 Thermal Conditions  
In July 2023, the mean T\({}_{\rm max}\) in Lublin was 25.3 \({}^{\circ}\)C, presenting an anomaly of +0.64 \({}^{\circ}\)C relative to the long-term average (Figure 3). This value was positioned at the 64 th percentile, closer to the upper quartile. The linear trend for T\({}_{\rm max}\) in July from 1991 to 2023 indicated an increase of 0.5 \({}^{\circ}\)C per decade; however, this trend was not statistically significant (\(p\) = 0.137). In August 2023, the mean T\({}_{\rm max}\) in Lublin was 26.3 \({}^{\circ}\)C, showing a positive anomaly of +1.91 \({}^{\circ}\)C compared to the long-term average and placing it at the 85 th percentile. The linear trend for T\({}_{\rm max}\) in August suggested an increase of 0.8 \({}^{\circ}\)C per decade, a statistically significant trend (\(p\) = 0.017), indicating a clear upward pattern in the August T\({}_{\rm max}\) in Lublin since 1991. In September 2023, the mean T\({}_{\rm max}\) in Lublin reached 23.6 \({}^{\circ}\)C, with a positive anomaly of +4.98 \({}^{\circ}\)C relative to the long-term average (Figure 3), placing it at the 100 th percentile and marking it as the highest recorded value for September in the analysed period. While the linear trend suggested an increase in September T\({}_{\rm max}\) by 0.81 \({}^{\circ}\)C per decade, this trend was not statistically significant (\(p\) = 0.097).  
The daily mean temperature (T\({}_{\rm avg}\)) in July and August in central Lublin was 1.0 \({}^{\circ}\)C higher than in the Botanical Garden located on the northwestern outskirts of the city. In July, the highest T\({}_{\rm avg}\) was recorded on 16 July, reaching 27.5 \({}^{\circ}\)C at Liteski Square and  
Figure 3: Multi-year variability and anomalies of T\({}_{\rm max}\) in Lublin in July, August, and September during the period 1991–2023.  
26.5 \({}^{\circ}\)C in the Botanical Garden (Figure 4a,b). On the same day, the highest T\({}_{\text{max}}\) was also observed, with values of 33.7 \({}^{\circ}\)C and 31.3 \({}^{\circ}\)C, respectively. In July, neither station recorded a T\({}_{\text{min}}\) > 20 \({}^{\circ}\)C. In August, the highest T\({}_{\text{avg}}\) and T\({}_{\text{max}}\) occurred on 15 August, with values of 26.9 \({}^{\circ}\)C and 34.7 \({}^{\circ}\)C in the city center and 25.8 \({}^{\circ}\)C and 33.3 \({}^{\circ}\)C in the Botanical Garden, respectively. Notably, in August, there were 12 days with a T\({}_{\text{max}}\) > 30 \({}^{\circ}\)C at Litewski Square, including a sequence of 9 consecutive days (from 13 to 21 August). This heat wave was accompanied by 4 tropical nights (T\({}_{\text{min}}\) > 20 \({}^{\circ}\)C) (Figure 4a). In the Botanical Garden, there were 9 days with a T\({}_{\text{max}}\) > 30 \({}^{\circ}\)C, of which 7 were consecutive (14-20 August), with one tropical night (Figure 4b). In September, the highest T\({}_{\text{max}}\) was recorded on 13 September, reaching 29.6 \({}^{\circ}\)C at Litewski Square and 29.2 \({}^{\circ}\)C in the Botanical Garden. During this month, neither station recorded any days with a T\({}_{\text{max}}\) > 30 \({}^{\circ}\)C or tropical nights.