Poland's weather patterns are made transitional and variable by the collision of diverse air masses above the country's surface. The wind in Europe comes from the Maritime air that moves across Western Europe from the North Atlantic Ocean. The Arctic air sweeps down from the north and the subtropical air arrives from the south. The warm currents and moderate temperatures associated with the polar air can cause precipitation, clouds and fog. When the moderating influences are lacking, winter temperatures in mountain valleys may drop to a minimum of −20 °C (−4 °F).
The spring arrives slowly in March or April, bringing mainly sunny days after a period of alternating wintertime and springtime conditions. Summer is usually less humid than winter. The weather is going to be showers and thunderstorms followed by dry and sunny weather. This happens when the southern and eastern winds are blowing. Early autumn is generally sunny and warm, but it starts to get rainy and colder in November as winter begins. Winter, which may last from one to three months, brings frequent snowstorms but relatively low total precipitation.
The average temperature in the northeast is 6°C (42.8°F) and in the southwest is 10°C (50°F), but it can be much colder or hotter depending on the season. The mean temperature is below zero on the highest peaks. The Baltic coast, influenced by west winds, is cooler in the summer and warmer in the winter. In Poland, the temperature is very cold in the winter. The coldest temperatures are in the southeast, along the border with Ukraine. There, winter temperatures average 4.5°C below those in western Poland. Tarn is the hottest city in Poland.
The Spa-Park in the resort of Świnoujście is a great place to spend your summer. There are plenty of things to do, including swimming, sunbathing, and exploring the nearby forests.
However, the average temperatures are rising. There have been 19 Decembers without snow from 1980 to 2010, and 7 from 2000 to 2010. Since 1779, December 2006 was the warmest month in Poland. Over the last three decades, average temperatures in most of Poland rose by 3-5 degrees Celsius.
The average annual precipitation for the whole country is 600 mm (23.6 in), but isolated mountain areas receive as much as 1,300 mm (51.2 in) per year. The total is higher in the southern uplands than in the central plains. Poland gets most of its rain in the summer, with a few areas getting less than 500 mm (19.7 in) per year. The amount of precipitation that falls as snow varies depending on location. In the lowlands, about half of all precipitation falls as snow in winter. In the mountains, however, all of the precipitation falls as snow. On average, precipitation in summer is twice of that in winter, providing a dependable supply of water for crops. The growing season in the southwest is about 40 days longer than in the northeast.