As a result of intensifying climate change, extreme weather events and local conditions, the city of Bialystok is vulnerable to urban and river flooding, as well as a combination of both. In addition, increasing dense development with large sealed surfaces intensifies these phenomena. In 2023, buildings and urban areas covered 54.23% of the city's territory, showing a steady upward trend compared to previous years. In order to protect the population and environment of Bialystok, which is the capital of the Podlaskie Province in Poland, statistical analyses were carried out taking into account changes in atmospheric temperature, total annual rainfall and annual rainfall above 20 mm between 1993 and 2023 in order to examine possible climate changes and determine their trend. The research showed that the share of annual rainfall above 20 mm in the total annual rainfall over 30 years increased by 15%, showing an average increase of 5% every 10 years with a stable frequency of rainfall events. The correlation between average air temperatures and average rainfall above 20 mm per 10 years showed a fairly strong correlation between the factors studied. This indicates a significant impact of the urban heat island (UHI) on the growing threat of urban flooding due to higher precipitation. Due to partial limitations on the possibility of modernising the sewers in Bialystok, it is important to introduce retention reservoirs and increase the absorption area, which can store water while relieving the main rainwater receiver, which is the Biala River, and additionally enable water retention in the city, greater infiltration of rainwater into the ground, and reduce the urban heat island effect during droughts.