The poster presents the results of the analysis of weather-related mortality and car accidents in two big polish cities. They were analysed using bioclimatic classification of air pressure systems and atmospheric fronts by M. Baranowska, types of air masses, meteorological parameters and seven types of thermal human sense according to effective temperature. These searches confirm that different meteorological conditions are responsible for an increase of car accidents, different for the mortality excess. This is why there is no simple definition of oppressive weather because the result of research depends mainly on the kind of human reaction that was taken for correlation to weather. Among the air pressure systems only disturbances in high pressure, named as low embayment in high caused both, rise in car accidents and mortality. On the first days of low which appear over Poland the sudden increase of car accidents is always noted but mortality at the same time sometimes goes down. In a high, the weather in general is favourable for human, though the decrease of car accidents is more obvious than drop in mortality. Strong atmospheric fronts, apart from their type, always lead to the excess of car collisions, however deaths are more frequent only behind warm front, in warm sector of low, where oxygen pressure is going down. Only on days when several (2 or 3) atmospheric fronts crossing over central Poland the rise in both characteristics is observed. When considering the changes in meteorological parameters the highest number of car accidents occurred after the biggest day to day changes of air pressure, decreases up to 28 hPa and rises of 11 hPa, without any dependence to air temperature changes. On the contrary mortality was not related to changes in air pressure but it was strongly correlated to air temperature. An increase of mortality rate was noted according to big rise of air temperature (of 14°C) and the highest number of deaths in Warsaw in 1994 was noted during the heat wave, formed in subtropical, extremely hot and hardly polluted, air mass. Driving a car needs high concentration of mind and proper body position that may cause both, fatigue of nervous system and muscle tension. That is why number of car accidents grows during the weather that dampen physical reactions, when sleepiness, tiredness, the weakening of straight reaction or its big variations appeared. What is interesting, if the meteorological phenomena like: rain or fog, commonly known as those which disturb in driving do not appear with active weather they do not cause any access in car accidents. Due to the studies: µ Bigger amount of car accidents occurs on days with big weather disturbances (especially in air pressure) and lesser inflow of solar radiation, when the time of reaction for the light signal is lengthen. µ The highest excess of mortality appears in extreme hot or cold air as a result of impaired thermoregulation, when the body cannot cope with oppressive weather.