Temperature: heat and frost
The average annual temperature in Poland ranges from 5-7*C in the hilly Pomeranian and Masurian lake districts and in the uplands to 8-10*C in the belt of the sub-Carpathian basins, the Silesian Lowland and the Wielkopolska Lowland. Only in the upper parts of the Carpathians and Sudetes is it about 0*C (Kasprowy Wierch, -0.8*C; Mt Sniezka, -0.4*C).
The hottest month is July with the average temperature standing at 16-19*C. The coldest area in July is the mountains, where the air temperature drops as the altitude increases (on average by 0.6*C for every 100 metres). In the summit areas of the Tatras and Sudetes, the average air temperature in July is just about 9*C. July is also cooler in areas adjacent to the Baltic (about 16*C), which is caused by the cold sea waters. The hottest area is central Poland, with the temperatures exceeding 18*C.
Hot days, when the temperature exceeds 25*C, occur from May to September. Their number increases the further you go from the sea. On average, there are only five such days at the Rozewie Cape and over 40 in the Sandomierz Basin and Lublin Upland.
The coldest month in Poland is January. Cold continental air flowing in from the east in January makes the eastern part of Poland one of the coldest areas in the country.
Sub-zero temperatures are recorded between November and March. The average annual number of frosty days ranges from about 25 along the lower Odra River and at the seaside to 65 in the Suwalki Lake District; in the mountains, it reaches 132 days on Mt Sniezka and 150 days on Kasprowy Wierch. The number of freeze days, typically in late spring and early autumn, ranges in the lowlands from 90 (at the seaside) to 130, while in the mountains it exceeds 200.
Varying air temperatures affect the length of the vegetation season, during which the average daily air temperature is at least 5*C. On average the vegetation season in Poland lasts about 200 days. It is the shortest in the mountains, in the eastern part of the Pomeranian Lake District and in the Masurian and Suwalki lake districts. It is the longest in the Silesian Lowland and along the lower Odra. The lowest temperatures ever recorded in Poland were -41*C in Siedlce (in 1940) and -40.6 *C in the Zywiec Basin (in 1929). The highest temperature, +40.2*C, was recorded in Pruszkow near Opole in 1921.
