Fig. 1.
Location of meteorological stations.
Table 1.
Threshold values of Humidex (koźmiński, Michalska 2013; http://www.rescuedynamics.ca/).
| Humidex [°C] | Levels of thermo-humidity discomfort | Heat syndrome |
|---|---|---|
| 20.0–29.9 | Comfort | Fatigue possible with prolonged exposure and/or physical activity |
| 30.0–39.9 | Slight discomfort | Heat stroke, heat exhaustion and heat cramps possible with prolonged exposure and/or physical activity |
| 40.0–45.9 | Great discomfort | Heat cramps or heat exhaustion likely |
| 46.0–54.9 | Dangerous | Heat stroke possible with continued exposure and/or physical activity |
| ≥55.0 | Heat stroke imminent | Heat stroke imminent with continued exposure |
Fig. 2.
Course of average Tmax in the summer seasons in the period 1966–2022 in Poznań (Poland) and Thessaloniki (Greece).
Table 2.
Characteristics of thermal conditions in the summer season in the period 1966–2022.
| Month | Tmax | Lowest average Tmax | Highest average Tmax | |||
|---|---|---|---|---|---|---|
| Average | Changes | Value | Year | Value | Year | |
| [°C] | [°C/Decade] | [°C] | [–] | [°C] | [–] | |
| Poznań | ||||||
| May | 19.5 | 0.23* | 14.6 | 1991 | 23.7 | 2018 |
| June | 22.7 | 0.51 | 18.9 | 1984 | 29.9 | 2019 |
| July | 24.5 | 0.46 | 19.9 | 1979 | 30.7 | 2006 |
| August | 24.2 | 0.51 | 20.4 | 1987 | 29.4 | 2015 |
| September | 19.1 | 0.34 | 14.7 | 1996 | 23.6 | 2016 |
| Summer | 22.0 | 0.41 | 19.3 | 1980 | 25.2 | 2018 |
| Thessaloniki | ||||||
| May | 24.9 | 0.25 | 21.8 | 1980 | 28.1 | 2013 |
| June | 29.5 | 0.40 | 26.7 | 2015 | 32.6 | 2012 |
| July | 31.9 | 0.42 | 29.4 | 1969 | 36.0 | 2012 |
| August | 31.7 | 0.52 | 28.0 | 1976 | 34.9 | 2012 |
| September | 27.6 | 0.23 | 24.6 | 2014 | 31.1 | 1994 |
| Summer | 29.1 | 0.37 | 26.9 | 2014 | 31.9 | 2012 |
Fig. 3.
The 90th percentile value of Tmax in the summer seasons in the period 1966–2022.
Fig. 4.
Number of hot days in the period 1966–2022.
Fig. 5.
Number of heatwaves (A), duration (B), and share of heatwaves by duration (C) in the period 1966–2022.
Table 3.
Characteristics of thermal conditions during heatwaves.
| Parameter | Poznań | Thessaloniki | ||
|---|---|---|---|---|
| Average | Date | Average | Date | |
| [°C] | [°C] | |||
| Average Tmax | 30.3 | – | 35.0 | – |
| Lowest average Tmax | 25.5 | 24–27 September 2006 | 29.1 | 4–7 May 2018 |
| Highest average Tmax | 35.5 | 19–21 July 2022 | 40.0 | 22–25 July 2007 |
| Highest Tmax | 38.0 | 26 June 2019 | 43.3 | 25 July 2007 |
| Average Tmax – longest heatwaves | 33.9 | 23 July–2 August 1994 | 37.3 | 8–18 August 2010 |
Table 4.
Characteristics of biometeorological conditions during heatwaves.
| Parameter | Poznań | Thessaloniki | ||
|---|---|---|---|---|
| Average | Date | Average | Date | |
| [°C] | [°C] | |||
| Average Humidex | 30.8 | – | 38.7 | – |
| Lowest average Humidex | 23.4 | 18–20 May 2017 | 29.1 | 8–10 May 2007 |
| Highest average Humidex | 38.2 | 15–17 July 2007 | 47.8 | 5–8 July 1988 |
| Highest Humidex | 39.8 | 26 June 2019 | 53.4 | 23 July 1987 |
| Average Humidex – longest heatwaves | 35.0 | 23 July–2 August 1994 | 43.5 | 8–18 August 2010 |
Fig. 6.
Frequency of occurrence of particular Humidex values during heatwaves in the period 1966–2022.