Poland must be considered as a transition region between Central and Eastern Europe also with regard to the climate, which on the whole is temperate continental, characterized by very strong annual excursions, which generally increase gradually which advances towards the east, and from the Baltic coasts towards the interior (annual excursion of 18 °, 4 to Hel, on the Baltic, of 20 °, 7 in Poznań, of 22 °, 5 in Warsaw, of 22 °, 7 a Lviv, of 24th, 4 in Pińsk). Temperatures are influenced by the distance of the sea, latitude and height. Thus Hel in the coldest month, January, has −1 °, 1; Poznań (210 m from the coast), −1 °, 9; Lviv (more than 600 km. From the sea), −4 °, 0 (and Lviv, if it is located at 338 msm, is however almost 5 ° of latitude more to S. di Hel); in the hottest month, July, the influence of the sea is inverse, that is, it maintains the lowest temperatures (Hel 17 °, 2, Poznań 18 °, 8, Lviv 18 °, 7). To show the influence of latitude it will be sufficient to compare the data from Vilna (106 msm, 54 ° 41 ′ N.) and Warsaw (125 msm, 52 ° 14 ′ N.): in January there are respectively −5 °, 0 and −3 °, 6; in July, 18th, 7th and 18th, 9. For the influence of height, the data from Krakow, Poronin and Jablonica can be compared. The first is located at 220 meters above sea level and has −3 °, 3 in January and 18 °, 7 in July; Poronin, at 740 m., Has respectively −5 °, 9 and 15 °, 3; Jablonica, at 900 m., Has −8 °, 5 and 4 °, 7. in January we have −5 °, 0 and −3 °, 6 respectively; in July, 18th, 7th and 18th, 9. For the influence of height, the data from Krakow, Poronin and Jablonica can be compared. The first is located at 220 meters above sea level and has −3 °, 3 in January and 18 °, 7 in July; Poronin, at 740 m., Has respectively −5 °, 9 and 15 °, 3; Jablonica, at 900 m., Has −8 °, 5 and 4 °, 7. in January we have −5 °, 0 and −3 °, 6 respectively; in July, 18th, 7th and 18th, 9. For the influence of height, the data from Krakow, Poronin and Jablonica can be compared. The first is located at 220 meters above sea level and has −3 °, 3 in January and 18 °, 7 in July; Poronin, at 740 m., Has respectively −5 °, 9 and 15 °, 3; Jablonica, at 900 m., Has −8 °, 5 and 4 °, 7. For Poland 2006, please check computergees.com.
The maximum temperatures are 35-37 °, the minimum ones around −30 ° in eastern Poland, around −25 ° in western Poland, where oceanic influence is still felt.
The barometric pressure in winter is increasing from NO. to SE. (influence of the high pressures of Siberia and Central Asia and of the low pressures that overhang the North Atlantic), while in summer it generally increases from NE. to SW. (influence of the Atlantic maximum and the continental minimum). The average annual pressure falls in bulk from S. to N. (Lviv 762.7; Warsaw 761.9; Vilna 761.8: values reduced to sea level). As a consequence of the isobaric trend just mentioned, there is a prevalence of SF winds, cold and dry, from January to March; strong westerly winds from June to September. In spring, winds mainly blow NW. in Poland west of the Vistula, while in the east, SE winds prevail. In autumn the most frequent winds are the southern ones. The violence of the winds as a whole decreases from N. to S., and this as a consequence of the increase of the average annual pressure from S. to N. and due to the influence of the sea in the north and the Carpazî in the south. Stronger winds usually blow from November to March.
Relative humidity is highest (87-90%) in December (western Poland) or November (eastern Poland), lowest (68-70%) in May (western Poland) or June (eastern Poland). The average annual relative humidity, as is known, generally decreases from the sea towards the interior regions: but this does not seem to occur in Poland, as far as we know so far.
The nebulosity, which averages 6-7 tenths, has its maximum in December (around 8) and its minimum in August (5-6). The insolation on the whole is deficient: Warsaw has 1570 hours of sunshine annually (Rome 2362 hours); the daily average is 4 and a half hours (1½ in winter, 4½ in spring, 8 in summer, 3½ in autumn); Poznań has 1758 hours of sunshine, Krakow 1796.
Precipitation is very unevenly distributed, ranging from areas with less than 500 mm. per year in areas with over 1200 mm. The first are four: the middle basin of the Vistula, to the west of Warsaw, the high basin of the Noteć, the middle basin of the Warta and the Polessia to the east of Pińsk. The greatest precipitations fall on the Carpazî, where they generally increase with height (Krakow, at 220 m., 735 mm.; Poronin, at 740 m., 922 mm.; Zakopane, at 850 m., 1230 mm.). Most of the country has between 500 and 700 mm. of precipitation, which on the whole increase from N. to S. in western Poland and vice versa in eastern Poland (Hel 489 mm., Bydgoszcz 511, Warsaw 541, Leopoli 690; Vilna 592; Pińsk 533, etc.) and are mainly summer (on average, 38% of the total: Poznań 35%, Warsaw 38, Pińsk 44, Bydgoszcz 36, Lviv 39, etc.). The driest season is winter (13-18 ° 6 of the annual total); the intermediate seasons receive 20 to 24% of rainfall. The abundant summer rains are brought by the westerly winds, laden with humidity.
Snowfall constitutes an ever higher percentage of total precipitation proceeding from W to E., and this is due to the lowering of winter temperatures. In Warsaw they represent 18% of the total (106 mm. Per year) and the days with snow are 58 (Hel 41, Poznań 40, Krakow 53, Lviv 59).