    
Climate
Poland has a moderate climate with both maritime and continental elements.
This is due to humid Atlantic air which collides over its territory with
dry air from the Eurasian interior. As a result, the weather tends to
be capricious and the seasons may look quite different in consecutive
years. This is particularly true for winters, which are either wet, of
the oceanic type, or - less often - sunny, of the continental type. Generally,
in north and west Poland the climate is predominantly maritime, with gentle,
humid winters and cool, rainy summers, while the eastern part of the country
has distinctly continental climate with harsh winters and hotter, drier
summers.
Poland's climate is chiefly shaped by air masses that come over its territory.
In summer, humid polar-maritime air from the north Atlantic brings clouds,
precipitation and cold weather, whereas in winter it causes thaw and fog.
Relatively dry polar-continental air from Russia, which typically comes
to Poland in winter, brings frosts while in summer it is responsible for
heat periods. Arctic air from far north (the Arctic Sea) produces changeable
weather and sudden temperature drops such as freezes in May. Tropical
air brings clouds and rains in summer and thaws and fogs in winter - so
it is similar to polar-maritime air although it flows in from the distant
Azores. Tropical air may also come from Africa or Asia Minor; it is of
the continental type and appears only in early spring and summer, bringing
hot and sunny weather.
Generally, Poland receives all kinds of air masses typical of the northern
hemisphere. This results in a variable climate and considerable problems
with weather forecasting. Poland's climate is also characterized by substantial
weather changes in consecutive years, caused by disturbances in the pattern
of main air masses coming to the country. Summer may be hot and dry a
few times in a row and then it becomes cool and wet. This phenomenon tends
to happen in several-year cycles.
Poland's climate is also strongly influenced by the lowland topography
of this part of Europe, stretching from France to Ukraine. Not stopped
by any natural barriers, air masses move quickly from the Atlantic or
North Sea. Another factor is the country's location, far from vast water
bodies (the Atlantic Ocean) and close to extensive land areas (Eurasia).
The Baltic Sea is a major contributor to the climate of north Poland while
the southern part of the country is also affected by the Black Sea.
 Winds
The main pressure systems that affect the weather are the Icelandic low
(stronger in winter) and the Azores anticyclone (more active in summer)
as well as the changing atmospheric fronts from Asia: the East Asian high
in winter and the South Asian low in summer. For a major part of the year
Poland has predominantly west circulation of winds, caused by the eastward
movement of barometric lows from the Atlantic. As a result, on 60 percent
of all windy days the winds are from the west, blowing mainly from the
area stretching between the Czech Republic and Scandinavia. In the eastern
part of the country, the percentage of easterly winds is higher, while
in the mountains, southerly winds occur more frequently.
The wind pattern is not uniform throughout the year. In summer months,
that is from July to September, the winds are mainly westerly, whereas
in winter, notably in December and January, easterly winds prevail. In
the transitory seasons, both winds occur roughly with the same frequency.
The winds in Poland are typically weak to moderate, their speed ranging
from 2 to 10 m/s. Strong and very strong winds occur at the seaside, causing
storms, and in the mountains, where their speed may exceed 30 m/s. Hurricanes
that uproot trees and blow off roofs are rather unusual. With its diversified
topography, Poland also has local winds. Along the Baltic coast, on a
cloudless summer day you can experience a pleasant, invigorating sea breeze
which occurs during the day and is felt about 10km inland. At night its
direction reverses: the air moves from the cooler land towards the warmer
sea, causing the land breeze.
In the mountains, there are mountain-valley winds. The best-known one
is the halny, which blows in the Tatras and has been the subject of many
poems and paintings. This kind of wind is not unique to Poland, though;
it occurs in all mountains around the world and is called the fÃÅ›hn. The
halny is strong and gusty and its effects are higher temperature and lower
air humidity on the leeward slopes. It develops when moving air is stopped
by a mountain range and forced to rise. The halny is a nuisance for people
as it lowers their mental and physical fitness and makes them irritable.
It is strong enough to break trees, sometimes over large areas, blow off
roofs and knock over fences. In winter it causes sudden thaws leading
to floods.
Cloudiness
and precipitation
A visible effect of the collisions of air masses above Poland is cloudiness.
The number of cloudy days is between 60 and 70 percent, which is relatively
high. Clouds may lead to precipitation. Fortunately, not all kinds of
clouds coming to Poland drop rain or snow. The sky is the most overcast
in November and the least in August and September. The most cloudy regions
are the lake districts in the north and the Sudetes; the least cloudy
are Wielkopolska and the Silesian Lowland. The average number of cloudy
days a year, with the sky more than 80% overcast, is 120-160; for sunny
days, with cloudiness below 20%, it is 30-50.
The heaviest precipitation in Poland was recorded in June 1973 in the
Tatra's Hala Gasienicowa. During one rain as much as 30cm of water fell.
Forty years earlier Podhale's village of Witow saw an almost as heavy
precipitation, lower by just 1.5cm.
Precipitation level depends not only on where the air masses come from,
but also on the altitude and slope direction. With Poland's predominantly
westerly winds, the highest precipitation occurs on western slopes of
mountains and hills. In the Carpathians and Sudetes, the annual precipitation
is 800-1400mm. In the lowlands and uplands, it ranges between 400mm and
750mm. Similar levels are recorded in the Pomeranian and Masurian lake
districts. This is caused by the proximity of the Baltic Sea, from which
humid sea air flows east. The lowest precipitation occurs in the eastern
part of Wielkopolska and in Kujawy, a region lying in the rain shadow
of the Pomeranian Lake District.
The maximum precipitation is in summer. At this time of the year it is
on average 2-3 times higher than in winter (in the Carpathians, as much
as four times higher). The smallest seasonal differences are recorded
in the coastal lowlands.
Winter comes to Poland from the north-east. The average annual number
of days with snowfall is 30-40 in the country's western and central part,
and over 50 days in the north-east. It snows for 120 days a year in the
Karkonosze and for 145 days in the Tatras. Snow stays the longest in the
mountains (up to 200 days) and in north-west Poland (90-120 days). The
western part of the country has the fewest days with snow cover (40-50).
Temperature
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).
So, except for the mountains, the regional differences of average temperatures
are small.
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.
Mean July isotherms run more or less parallelly, their value decreasing
northwards from over 18.5°C in the Silesian Lowland, south Wielkopolska
and the Sandomierz Basin to 16.5°C in the Kashubian Lake District. 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. The air temperature decreases
eastwards and the isotherms run almost meridionally. Milder winters in
the west are the result of warm air masses from the Atlantic. The further
east you go, the weaker this influence is and the number of frosty days
rises. 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.
Seasons
Poland has as many as six distinct seasons. Apart from the four typical
European seasons, there are also two periods described as early spring
(przedwiosnie) and early winter (przedzimie). The seasons hardly conform
to the calendar pattern. During the przedwiosnie, which is about a month
long, the average daily air temperature ranges from 0°C to 5°C. Spring
in Poland lasts usually about 60 days and comes from the west. The daily
temperature at that time ranges from 5°C to 15°C. This is also when the
vegetation season begins in Poland. The long-awaited summer, with temperatures
above 20°C, begins in May and is about four months long. In autumn, the
average temperature drops to between 5°C and 15°C. Sometimes the season
is kind and allows the Poles to enjoy more sunshine. Almost every year,
mid September sees the coming of Polish "Indian summer", which is a warm
and sunny transition between summer and autumn. Leaves start to fall off
the trees, but you can still feel the wafts of warmth.
Once the trees have lost all their leaves and the days are markedly shorter,
przedzimie begins. Temperatures drop below 5°C. After about six weeks,
winter comes and the frosts don't want to go away for a long time - until
late February or early March, and even then przedwiosnie can be felt only
in Pomerania and west Poland. The highlanders have to wait for it until
mid March, while in the north east early spring arrives another two weeks
later.
The seasons are of different length in every geographical region. For
instance, summer in north Poland lasts about 2.5 months, while in the
south east, centre and south west of the country it is over three months
long. Winter length ranges from two months at the seaside and in the west
to 3-4 months in the north east and even six months in the Tatras.
This climatic calendar is more complicated, though, as there are plenty
of anomalies which make another distinctive feature of Poland's climate.
There are many proverbs about the unpredictable weather, especially in
March and April. Przedwiosnie may arrive as early as at the beginning
of February and, conversely, it can sometimes snow even in September.
In January 1982 the air temperature in Wloclawek dropped overnight from
8°C to -20°C, the record drop since temperatures started to be officially
recorded in Poland. On 8 January 1994 the temperature in Cracow's centre
stood at 17.3°C.
The
hottest and coldest areas
The hottest part of Poland is the Silesian Lowland, strongly influenced
by the Atlantic air. An important factor is also the region's location
close to higher-lying areas that stop clouds and moisture, which results
in high insolation. Air masses from the Atlantic raise temperatures in
winter. Average temperatures in January exceed -1.5°C and are among the
highest in Poland. The thermal winter period here is only about 60 days
long and winters are relatively mild, while summers are sunny and hot,
lasting over 100 days, which puts them among the longest in Poland. Average
temperature in July exceeds 18.5°C. The highest temperatures are recorded
near Wroclaw, on the Wroclaw Plain. This is the only area in Poland where
the annual average temperature is over 8.5°C. Because of this mild climate,
the Silesian Lowland has one of the longest vegetation seasons in the
country, lasting 220 days.
The coldest spot is the north-eastern corner around Suwalki. With its
morainal hills, postglacial lakes and low temperatures, this region bears
much similarity to the distant Scandinavia. Harsh and long winters, lasting
over four months, earned it the name of Poland's cold pole. The influence
of the continental climate manifests itself in very low temperatures in
winter and pretty high ones in summer. The average temperatures in the
Suwalki region have the biggest amplitudes in Poland, over 23°C, which
is even more than in the mountains. The average air temperatures in January,
the coldest month, are below -5°C, the lowest in Poland. In summer the
average air temperature drops below 17.5°C. The annual average air temperature
in the Suwalki Lake District is slightly more than 6°C. Predictably, summer
here is one of the shortest in Poland, lasting about 60 days. The vegetation
season in this harsh climate is about 190 days long, to which the breathtaking
wild nature of the Suwalki region has become well adapted.
Areas
with the lowest and highest precipitation
Paradoxically, the driest part of Poland is a region abounding in lakes
and rivers - Kujawy. As it lies in a rain shadow, it sees relatively rare
rains and snowfalls. Before reaching Kujawy and west Wielkopolska, the
prevailing north-west air masses lose their moisture above the higher-lying
Pomeranian Lake District. Other factors are the flatness of the terrain
and the lack of any sizeable forests. At Lake Goplo, the yearly precipitation
is just 300mm, which is the lowest value in the country.
Radically different are the Tatras, where rain, snow or even hail is
more likely than sunshine. Rocks and plants are often covered by hoar-frost,
rime or dew, collectively referred to as horizontal precipitation. Water
circulation in this area is particularly intense. Retained for a short
time by the mountains or by a snow cover, water escapes quickly as fog
or through crystal-clear mountain streams.
The Tatras have the highest precipitation in Poland. This is particularly
evident in the Five Lakes' Valley (Dolina Pieciu Stawow Polskich), where
the annual precipitation exceeds 1800mm of water. The period from April
to October has more precipitation than the winter half-year. June is usually
the rainiest month of the year, while February is the least likely month
for any precipitation (in high mountains, it is September). On Kasprowy
Wierch, there are annually about 230 days with daily precipitation over
0.1mm and about 50 days when it exceeds 10mm. The mount also has the longest-lying
snow cover. Some snow is blown by winds and when it is warm enough, water
evaporates intensively, which makes an impressive sight.
In winter, the Tatras see a curious phenomenon known as temperature inversion.
In the valleys, it is colder than in the higher parts of the mountains.
The so-called fog seas that develop in depressions make the air above
extremely clear, so that the views from the peaks extend over hundreds
of kilometres.
Source: www.poland.gov.pl
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