Table 1.
Thermal stress categories based on the Universal Thermal Climate Index (Błażejczyk et al. 2010).
| UTCI (°C) | Stress category and recommendations for protection |
|---|---|
| > 46.0 | extreme heat stress, periodical cooling and drinking > 0.5 l • h–1 necessary, stay without activity |
| 38.1 to 46.0 | very strong heat stress, periodical use of air conditioning or shaded sites and drinking > 0.5 l • h–1 necessary, reduce activity |
| 32.1 to 38.0 | strong heat stress, drinking> 0.25 l • h–1 necessary, use shade places and reduce activity |
| 26.1 to 32.0 | moderate heat stress, drinking> 0.25 l • h–1 necessary |
| 9.1 to 26.0 | no thermal stress, physiological thermoregulation sufficient to keep comfort |
| 0.1 to 9.0 | slight cold stress, use gloves and cap |
| −13.0 to 0.0 | moderate cold stress, increase activity, protect extremities and face against cooling |
| −27.0 to −12.9 | strong cold stress, strongly increase activity, protect face and extremities, use better insulated clothing |
| −40.0 to −26.9 | very strong cold stress, strongly increase activity, protect face and extremities, use better insulated clothing, reduce stay outdoor |
| < −40.0 | extreme cold stress, stay in door or use heavy, wind protected clothing |
Fig. 1.
Location of stations in Poland used in the study.
Fig. 2.
Median, lower and upper quartiles and average minimum and maximum Universal Thermal Climate Index at 12:00 UTC in Kołobrzeg, Poznań and Kraków (1951–2020).
Fig. 3.
Frequency of thermal stress based on the Universal Thermal Climate Index at 12:00 UTC in successive months recorded in Kołobrzeg, Poznań and Kraków (1951–2020). Legend: <−40 (extreme cold stress) −40 to −27 (very cold stress) −27 to −13 (strong cold stress)−13.0 to 0.0 (moderate cold stress)0.0 to 9.0 (slight cold stress) 9.0 to 26.0 (no thermal stress) 26.0 to 32.0 (moderate heat stress) 32.0 to 38.0 (strong heat stress) 38.0 to 46.0 (very strong heat stress).
Table 2.
Annual and monthly values making the multi-annual trend (1951–2020) and 10-year Universal Thermal Climate Index measured at 12:00 UTC in Kołobrzeg, Poznań and Kraków. Values with a statistical significance level of 0.05 are marked in bold type.
| City | Kołobrzeg | Poznań | Kraków | |||
|---|---|---|---|---|---|---|
| Month | 1951–2020 | per 10 years | 1951–2020 | per 10 years | 1951–2020 | per 10 years |
| 1 | 5.4 | 0.8 | 4.8 | 0.7 | 3.6 | 0.5 |
| 2 | 6.6 | 0.9 | 5.3 | 0.8 | 6.8 | 1.0 |
| 3 | 7.3 | 1.0 | 6.6 | 0.9 | 7.0 | 1.0 |
| 4 | 6.1 | 0.9 | 7.6 | 1.1 | 5.9 | 0.8 |
| 5 | 5.8 | 0.8 | 5.1 | 0.7 | 5.3 | 0.8 |
| 6 | 3.9 | 0.6 | 2.2 | 0.3 | 3.9 | 0.6 |
| 7 | 4.3 | 0.6 | 4.7 | 0.7 | 4.5 | 0.6 |
| 8 | 5.2 | 0.7 | 5.2 | 0.7 | 4.8 | 0.7 |
| 9 | 4.0 | 0.6 | 2.1 | 0.3 | 1.9 | 0.3 |
| 10 | 3.5 | 0.5 | 1.6 | 0.2 | 2.5 | 0.4 |
| 11 | 5.6 | 0.8 | 4.4 | 0.6 | 3.8 | 0.5 |
| 12 | 4.3 | 0.6 | 3.2 | 0.5 | 2.8 | 0.4 |
| year | 5.2 | 0.7 | 4.4 | 0.6 | 4.4 | 0.6 |
Fig. 4.
Multi-annual curve of the minimum and maximum values, lower quartile (Q1) and upper quartile (Q3) and the trend line of the Universal Thermal Climate Index at 12:00 UTC in Kołobrzeg, Poznań and Kraków (1951–2020).
Fig. 5.
Multi-annual thermal stress curve at 12:00 UTC including trend line, based on the Universal Thermal Climate Index in Kołobrzeg, Poznań and Kraków (1951–2020).
Table 3.
Annual and monthly linear trend values recorded at 12:00 UTC for the frequency of respective types of thermal stress in Kołobrzeg, Poznań and Kraków (1951–2020). Values with a statistical significance level 0.05 are marked in bold type.
| Month | Extreme, very strong and strong cold stress | Moderate and slight cold stress | No thermal stress | Moderate heat stress | Strong and very strong heat stress |
|---|---|---|---|---|---|
| Kołobrzeg | |||||
| 1 | −30.7 | 30.9 | 2 cases | – | – |
| 2 | −33.4 | 32.3 | 1.1 | – | – |
| 3 | −27.0 | 21.9 | 5.2 | – | – |
| 4 | −8.4 | −14.5 | 22.3 | 0.4 | 1 case |
| 5 | −1.1 | −29.1 | 26.6 | 3.3 | 0.3 |
| 6 | – | −12.8 | 5.8 | 5.3 | 1.7 |
| 7 | – | −6.7 | −11.8 | 15.5 | 2.9 |
| 8 | – | −11.3 | −7.2 | 14.6 | 3.9 |
| 9 | 3 cases | −17.4 | 13.7 | 4.4 | −0.4 |
| 10 | −0.6 | −17.6 | 18.7 | −0.5 | – |
| 11 | −14.4 | 9.2 | 5.2 | – | – |
| 12 | −18.3 | 18.7 | −0.4 | – | – |
| year | −11.1 | 0.1 | 6.5 | 3.6 | 0.8 |
| Poznań | |||||
| 1 | −26.4 | 26.0 | 0.4 | – | – |
| 2 | −28.8 | 28.3 | 0.4 | – | – |
| 3 | −29.8 | 24.1 | 5.8 | – | – |
| 4 | −12.3 | −9.8 | 21.4 | 0.8 | 1 case |
| 5 | −1.3 | −19.5 | 16.9 | 3.9 | 0.2 |
| 6 | – | −9.1 | 5.2 | −1.3 | 5.3 |
| 7 | – | −12.7 | −1.3 | 8.0 | 6.0 |
| 8 | – | −14.3 | −4.1 | 13.9 | 4.5 |
| 9 | 1 case | −11.6 | 13.0 | −0.7 | −0.6 |
| 10 | −1.4 | 0.9 | 0.7 | −0.3 | – |
| 11 | −13.9 | 10.5 | 3.4 | – | – |
| 12 | −20.9 | 20.9 | 0.0 | – | – |
| year | −11.2 | 2.7 | 5.1 | 2.1 | 1.3 |
| Kraków | |||||
| 1 | −13.8 | 11.5 | 2.3 | – | – |
| 2 | −21.9 | 12.5 | 9.5 | – | – |
| 3 | −17.0 | 3.8 | 13.4 | −0.2 | – |
| 4 | −1.8 | −20.1 | 17.6 | 4.0 | 0.4 |
| 5 | – | −20.1 | 5.2 | 11.4 | 3.5 |
| 6 | – | −7.9 | −10.6 | 9.0 | 9.5 |
| 7 | – | −3.9 | −19.1 | 7.2 | 15.8 |
| 8 | – | −2.4 | −22.8 | 4.9 | 20.3 |
| 9 | – | −7.9 | 2.5 | 6.4 | −1.0 |
| 10 | −0.6 | −5.8 | 0.5 | 6.0 | – |
| 11 | −4.5 | −7.7 | 12.3 | 1 case | – |
| 12 | −9.8 | 5.6 | 4.2 | – | – |
| year | −5.7 | −3.6 | 1.1 | 4.1 | 4.1 |