Aim of the study:
Rising and falling atmospheric pressure usually heralds changes in weather conditions such as temperature, air humidity, cloud cover, precipitation, and wind speed. The work presents variations of atmospheric pressure in Siedlce from 2001 to 2022. The objective of the present work is to analyse diurnal variations in atmospheric pressure, as well as the amplitude of fluctuations and trends.

Material and methods:
Daily atmospheric pressure values were obtained from a meteorological station of the Institute of Meteorology and Water Management (IMGW). Diurnal changes in atmospheric pressure causing different levels of strain on the human body, ranging from weak to very strong, were identified. For each month, the number of days with specific diurnal pressure changes was calculated. The trend in monthly pressure changes was determined based on linear regression equations.

Results and conclusions:
The average annual atmospheric pressure at sea level in Siedlce was 1016 hPa, the lowest and the highest recorded pressure values being, respectively, 928 hPa on 25th March, 2016, and 1051 hPa on 23rd January 2006. The difference between the highest and the lowest pressure values in a given month was the greatest in January and February (40 hPa), and the lowest in August (17 hPa). The summer months of July and August, classified as weak stimulus days, exhibited the greatest diurnal variation in atmospheric pressure, while December and January were classified as very strong stimulus days, because they showed the highest variation. Monthly atmospheric pressure values in Siedlce displayed no substantial tendency to change during the study period.