Karachi is the capital of the Pakistani province of Sindh. It is the most populous city in Pakistan, sixth most populous city proper in the world and the 8th most populous metropolitan city in the world. Ranked as a beta world city, the city is Pakistan's premier industrial and financial centre. Karachi is also Pakistan's most cosmopolitan city. Situated on the Arabian Sea, Karachi serves as a transport hub, and is home to two of Pakistan's two largest seaports, the Port of Karachi and Port Bin Qasim, as well as the busiest airport in Pakistan. Though the Karachi region has been inhabited for millennia, the city was founded as a fortified village named Kolachi in 1729. The settlement drastically increased in importance with the arrival of British East India company in the mid 19th century, who not only embarked on major works to transform the city into a major seaport, but also connected it with their extensive railway network. By the time of the Partition of British India, the city was the largest in Sindh with an estimated population of 400,000. Following the independence of Pakistan, the city's population increased dramatically with the arrival of hundreds of thousands of Muslim refugees from India. The city experienced rapid economic growth following independence, attracting migrants from throughout Pakistan and South Asia. Karachi has an arid climate dominated by a long "Summer Season" while moderated by oceanic influence from the Arabian Sea. The city has low annual average precipitation levels (approx. 250 mm (9.8 in) per annum), the bulk of which occurs during the July–August monsoon season. While the summers are hot and humid, cool sea breezes typically provide relief during hot summer months. The winter climate is dry and lasts between December and February. It is dry and pleasant relative to the warm hot season, which starts in March and lasts until monsoons arrive in June. Proximity to the sea maintains humidity levels at near-constant levels year-round.