Heat-related mortality during hot summers in Polish cities

The number of fatalities in some Polish cities was more than three times higher during the hottest days than the mean mortality at the same date in years without a heat wave. The number of additional deaths in the largest cities increased noticeably when daily maximum air temperature exceeded 26-28 °C. The number of heat-related fatalities was highest in the summer of 1994: in the 10 largest cities of Poland, additional mortality was almost 1100 people.

The Polish results show that additional heat-wave-related mortality is compensated only slightly (up to 25%), or even not at all, by a decrease of the number of fatalities in the 30 days after the heat wave. The results are in line with conclusions of other studies that the increase of mortality risk during heat waves in Poland is particularly high for people older than 65 years and suffering from cardiovascular diseases.The excess mortality was highest during heat waves that were both intense and long lasting, with maximum air temperature exceeding 35°C and heat wave duration longer than 4 weeks. For long-lasting heat waves in urban conditions in Poland, their intensity seems to be of higher importance than their duration.

The results show that the increase of mortality during heat waves is a serious threat in Poland already in the present climate and will become even more severe in a warming climate. The authors conclude that decision-makers and the broad public in Poland are underestimating the Risk and that current warning systems are not adequately designed to properly inform the population.