A little more detail on this node. First of all, note that I refer to the range as the Tatry, not Tatry Mountains. Unlike say "Rocky Mountains", where "Mountains" is part of the proper name, "Tatry" is self-contained. In Polish, the word is pronounced "Tah-tryy", where the "tr" sound is hard, not English soft (not like train or try at all - unfortunately there is no word in English that actually pronounces the t within the tr construct). Try to enunciate the t and the r distinctly, and you'll get it.

Specs

Highest peak - Gerlach, 2665m asl.
Length - 80km (55 miles) along the main ridge
Width - Avg 15km (10miles), max 19km (12miles)
Area - 750 km²
Interesting fact: The Tatry form Eastern Europe's continental divide; the northern part sends rivers (Poprad, Dunajec) to the Baltic Sea; the southern (Váh / Wag, Orava/Orawa)to the Black Sea.

Description

The Tatry Mountains (2665 m maximum height, Gerlach) are the highest agglomeration in the entire Carpathian Mountains range. They are the tallest alpine-like range between the actual Alps and the Caucasus ranges, and between the Balkans and the mountains of northern Scandinavia. They are a miniature of true alpine mountains and as such, excellent for nearly all types of mountaineering and hiking (beginner to advanced, not quite mega uber hardcore expert K2 or Chomolungma though). They also house the largest natural concentration of flora and fauna in Eastern Europe, having biosystems ranging from lush, humid forests to barren moonscapes devoid of life. Both the Tatrzanski Park Narodowy (Poland) and Tatranski Narodny Park (Slovak Republic) - the names mean Tatra National Park in their respective languages - are recognized by the MAB World System of Biosphere Reserves.

The Polish Tatry are actually only 1/5th of the entire range; the main ridge - running more or less straight east to west - of the range is the national border however. The hundreds of hikers walking daily along the ridge do not need a visa when crisscrossing the border. The border itself is marked at regular intervals (about 100m) with white pillars capped with red paint; the pillars extend 1 meter above ground and are about 50cm wide x 50cm broad. In places where placing pillars would be impractical (say a 45° sheer rock incline), white and red weatherproof paint is applied to sizeable boulders. It is a unique and interesting sight.

Composition

The Tatry are divided into 3 parts based on their composition and the resulting climate and appearance. To the East we have the White Tatry, located primarily in Slovak Republic and composed of porous bedrock; in the center are the High Tatry, granite-boned and sky-reaching, and in the West are the appropriately named West Tatry (also called the Small Tatry), with gentler, sloping hills undercut by steep limestone cliffs. The Slovak names are Biele Tatry, Vysoke Tatry, and Male Tatry, respectively; the Polish Tatry Bielskie, Tatry Wysokie, and Tatry Zachodnie.

Weather

Mostly brisk and dry, and extremely susceptible to rapid change. Temperatures in the summer rarely go above 10°C, and the average for the year hangs around freezing (0°C). It is not unusual for snow to fall during the summer, and snow usually lays in shady spots year-round. If it's not snowing, it'll be raining - the Tatry are known to be capricious, and any day chosen for hiking may turn out to be rainy. A 50% chance of rain is the daily norm throughout the range, with a 66% chance being a constant in the higher parts. During the summer months the rains are usually abrupt and are accompanied by a drop in temperature. To put it simply, if you plan to hike, always always always take a rain jacket and a second layer of clothes, no matter what the prognosis. I have never hiked in the winter, but I would imagine it is not nice at all due to icing, low temperature, and heavy snowfalls.

The region is also known for the "halny" wind, a dry and warm wind which comes in from the mountains and blows north. It is very intense and unceasing, and can last from a few hours to a few days, ranging from 30kph to 100kph (20mph to 70mph) - the fastest ever noted was in 1965, clocked at 283kph; it of course changes the weather quite severely and abruptly, and can cause rapid snow melts and flash flooding. The wind is also unfriendly to humans' wellbeing, both mental and physical; it has been noted that there are more fights and suicides when it blows, and the incidence of heart attacks and strokes is increased. When it stops, it is invariably followed by thick cloud cover and precipitation. The strongest winds occur in the fall and winter, making them less of a factor for hiking tourists.

Flora

Due to the aforementioned variation in climates, the three zones are quite varied. The lowest is abundant in thick fir, spruce and maple forests (mixed); in the middle the spruce is dominant and thinner, above that is a well-defined layer of dwarf mountain pine, very thick and ranging in height from 1-1.5m. Above that is the domain of assorted grassy growth; you may also find moss and lichens. Finally, of course, there is nothing but rock. In some places the borders between these climates are well-defined, sometimes less-so.

Fauna

Unfortunately due to the explosive popularity of mountain hiking in Poland, the animal populations are ever decreasing, despite constant studies on prevention and preservation. For now you can still encounter the mountain goat or the marmot in the upper ranges, deer and brown bear in the lower - bears are especially active after dark. It is highly recommended you plan your trip to end at either a shelter or mountain base before it gets dark.

Local Info

For a few hikes and ideas on what to do in the mountains, I suggest starting with Zakopane; it is the premier vacation hotspot year-round, although mountain hiking is recommended in summer. The Tatry are also home to the excellent Tatran beer (Slovak Republic) brewed in Poprad, and the Żywiec brewery (Poland) brewed in Żywiec; the clear spring water is an excellent starting point for these fantastic pilsners. On the Polish side there are the skiing hotspots (well, sort of - the industry is not quite as well-developed as say, that of Taos or Crested Butte) of Zwardoń and Szczyrk; on the Slovak, there are Strbske Pleso and Stary Smokovec.

All the usual disclaimers apply. Enjoy your stay; don't feed the animals; don't pick firewood or flowers; don't litter; pack your trash; be aware of your surroundings, and remember, the paths are marked for your safety - straying not only harms the environment, but may harm you.
Sources:
http://www.zakopane.pl
http://www.tatry.sk
Experience