Multi-Annual Variations in the Heat Load of Poland

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Fig. 5.

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

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

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