15–20 days annually. In Bihar in middle of the Ganges plain, hot weather sets in and the summer lasts until the middle of June. The highest temperature is often registered in Late May or Early June which is the hottest time. Like the rest of the north, Bihar also experiences dust-storms, thunderstorms and dust raising winds during the hot season. Dust storms having a velocity of are most frequent in May and with second maximum in April and June. The hot winds (loo) of Bihar plains blow during April and May with an average velocity of . These hot winds greatly affect human comfort during this season. Rain follows. The rainy season begins in June. The rainiest months are July and August. The rains are the gifts of the southwest monsoon. There are in Bihar three distinct areas where rainfall exceeds . Two of them are in the northern and northwestern portions of the state; the third lies in the area around Netarhat. The southwest monsoon normally withdraws from Bihar in the first week of October. Eastern India's climate is milder but gets colder as one moves north west, experiencing moderately warm days to cool days and cool nights to cold nights. Highs ranges from 18°C to 23°C (64°F to 73°F) in Patna; to 22°C to 27°C (72°F to 80°F) in Kolkata (Calcutta); lows averages from 7°C to 10°C (45°F to 50°F) in Patna; to 12°C to 15°C (54°F to 59°F) in Kolkata. In Madhya Pradesh which is towards the south-western side of the Gangetic Plain similar conditions prevail albeit with much less humidity levels. Capital Bhopal averages low of and high of . Frigid winds from the Himalayas can depress temperatures near the Brahmaputra River. The Himalayas have a profound effect on the climate of the Indian subcontinent and the Tibetan plateau by preventing frigid and dry Arctic winds from blowing south into the subcontinent, which keeps South Asia much warmer than corresponding temperate regions in the other continents. It also forms a barrier for the monsoon winds, keeping them from travelling northwards, and causing heavy rainfall in the Terai region instead. The Himalayas are indeed believed to play an important role in the formation of Central Asian deserts such as the Taklamakan and Gobi. The mountain ranges prevent western winter disturbances in Iran from travelling further east, resulting in much snow in Kashmir and rainfall for parts of