Lake Balaton lies in the middle of Transdanubia, the west side part of Hungary. The surface of the water covers an area of 596 sq. km. At its longest point the lake stretches for 77 km, its coastline is 197 km long. The lake is 14 km wide at its widest point, and 1.5 km at its narrowest point (between Tihany and Szántód), its average width is 8 km. The water reaches an average depth of 2–3 m, though at Tihany it is 12.40 m deep.
Since the water of the lake warms rapidly, it is possible to swim there from spring to autumn. The water of the southern shore, being much shallower than that of the northern shore, sometimes reaches a temperature of 25 Celsius, and for that reason is a real paradise for children, the sands there have a velvety texture. The water of the northern shore becomes colder and the bottom of the lake is no longer covered with very fine sand. This is why the more popular resort areas are more numerous along the southern shore, where Balatonföldvár is located, too.
The origin of the lake goes back to the Tertiary Period, a time when the area of present Hungary was covered by sea. The remainder of this sea, Lake Pannon, gradually became filled with alluvial deposits of waters feeding into the lake, and later red-hot magma broke to the surface through fissures in the rocks underneath. As it cooled, the lava turned into basalt, and in those places where the basalt caps that were formed protected the layers underneath, neither wind, rainwater, nor streams on their way down could form channels in the deposits which were to become 3-400 m high mountains later on. After vulcanic activity in the area ceased, boiling waters gushed out of the fissures, and this is, for example, how the warm-water lake of Hévíz was formed. Effervescent springs finally appeared of which there are about twenty still in existence. The lake bed came into existence while the depressions were being formed about 22,000 years ago.
Lake Balaton is therefore a relatively recent lake. The lake bed was gradually filled by water fromprecipitation and inflowing streams, but at that time the lake was much larger than it is today and the surface of the water was 12 m higher. The water along the northern shore is provided by streams and on the southern shore mainly man-made canals. The Zala River provides the lake with the largest quantity of water. Today the volume of the lake is 1,800 million cubic metres, an amount which experts are trying to maintain.
At Siófok, for example, the water level, which should be maintained at 104 m 57 cm above the level of the Adriatic, is regulated by a lock. The Balatonąs soft, mildly alkaline water combines the effects of effervescent baths as well as those of sun-bathing and pelotherapy. Waves are relatively short (7–10 m) but strong and therefore dangerous during windy weather and storms (the highest wave so far measured reached 1.8 m). Storm approach is signalled by orange blinking lights, fastened on different buildings facing the lake. When seeing these signs swimmers and persons must stay close to the shore.
In winter the lake is mostly frozen over and it is suitable for winter sports as soon as the thickness of the ice reaches 15 cm. (The average thickness of the ice is between 25-30 cm, the thickest ice measured since the turn of the last century was 75 cm.) Vast expanses of reeds covering certain areas along the shores are characteristic of the type of vegetation found on the Balaton. When the lake is frozen over, the reeds are harvested with sharp push-scythes and used for building material as was the custom in the past. Seaweed, another characteristic form of vegetation, forms veritable fields in certain places. There are 42 different kinds of fish in the lake, the tastiest being the giant pike perch (fogas). A predatory fish living there is the European wels. The lake abounds in carp, razor-fish and bream.
The climate at the Balaton is agreeable, the number of summer days surpassing 25 Celsius averaging about 70, while the water Temperature in the summer is from 22 Celsius to 25 Celsius. The peak season in the summer lasts from June to the end of August. Solar radiation reflected from the surface of the water greatly increases the effects of sunlight and one should therefore exercise considerable caution when sunbathing.Sailing on the Balaton is more than 100 years old. Today there are almost 5,000 sail-boats from the smallest dinghy to large ships. The largest sporting event held every two years involves circumnavigating the lake for the Balaton Blue Ribbon.