(when the weather is often cloudy, cool, damp, rainy and/or snowy) to the occasional intrusions of cold air masses from Siberia or the Arctic (Siberian High), which, due to the city's northeasterly location, are more frequent than in other parts of Poland. Winters thus tend to be several degrees colder than elsewhere in Poland. Freezing conditions below are possible in winter but are rare. Snow cover is present on the ground for more than half of winter. Summers tend to be warm, sunny and pleasant and are occasionally hot, but they are still a little cooler than in most of Poland. More rain falls in summer months than in any other period of the year. The centre of Białystok, as most urban areas, experiences the urban heat island effect, therefore for most of the time, the city is warmer than the surrounding countryside. The temperatures in the city centre are, on average, higher than in the surrounding villages, with greater differences at night and during the warmer half of the year, particularly in spring. Urban layout Bialystok is roughly circular, centered around the old city Church Square and Branicki Palace. Originally, the city's territory was about 50 hectares. The communication system serving the entire city was made of streets radiating out from the central market square. An inventory plan made by Becker in 1799 was needed by the Prussian authorities in connection with the negotiations on the acquisition of Białystok for a royal residence. The plan is of fundamental importance as it shows the development of the city in the first period of its creation. The area of ​​the city did not exceed 1.5 km2, and the population was approx. 3.5 thousand. The entire urban area was closed with 6 loose-fitting gates and buildings situated on regular plots. Compact buildings were found only in the market square, the frontages of which were 1- 2-storey buildings with brick front elevations. Choroska and Zamkowa Streets were built up with only brick houses. The city was dominated by the palace complex, which, together with the park, covered an area equal to the city's investment areas. The residence palace was designed on a European scale and created new development opportunities for Białystok. After the First World War, the first attempts were made to organize the city, which had so far developed without plans - between the palace grounds and arable land. At the request