the watershed of the Godavari River and its tributary, the Indravati River. The Mahanadi is the chief river of the state. The other main rivers are Hasdeo (a tributary of Mahanadi), Rihand, Indravati, Jonk, Arpa and Shivnath. Forest The state has 3rd largest forest by area in India. The state animal is the van bhainsa, or wild Asian buffalo. The state bird is the pahari myna, or hill myna. The state tree is the Sal (Sarai) found in Bastar division. Chhattisgarh has the 3rd largest forest cover in the country. The state is surrounded by the forests in Madhya Pradesh (1st), Odisha (4th), Maharashtra (5th), Jharkhand and Telangana making it India's largest covered forests across state boundaries. There are multiple National Parks, Tiger Reserves across the state. Achanakmar-Amarkantak Biosphere Reserve is UNESCO recognised Biosphere with total area of 383,551 hectares (3835.51 km2). The natural environment of Koriya in Chhattisgarh includes forests, mountains, rivers and waterfalls. Koriya was a princely state during the British rule in India. Koriya is also known for its mineral deposits. Coal is also found in this part of the country. The dense forests are rich in wildlife. The Amrit Dhara Waterfall, Koriya's main attraction, is a natural waterfall which originates from the Hasdeo River. The fall is situated seven kilometres from Koriya on the Manendragarh-Baikunthpur road. The Amrit Dhara Waterfall falls from a height of 27 m, and it is approximately 3–4.5 m wide. Chirimiri is one of the most popular places, known for its natural environment and climate, in Chhattisgarh. Climate Chhattisgarh has a tropical climate. It is hot and humid in the summer because of its proximity to the Tropic of Cancer and its dependence on the monsoons for rains. Summer temperatures in Chhattisgarh can reach up to 49 °C (113 °F). The monsoon season is from late June to October and is a welcome respite from the heat. Chhattisgarh receives an average of of rain. Winter is from November to January. Winters are pleasant with low temperatures and less humidity. Ambikapur, Mainpat, Pendra Road, Samri and Jashpur are some of the coldest places in the state. Transport Roads Chhattisgarh has four-lane or two-lane roads that provide connectivity to major cities. A total of 20 national highways pass through the state, together measuring 3,078 km. Many national highways exist only on paper and are not fully converted into four-lane, leave alone six-lane or eight-lane,