latitude from 35° 35' to 37° 09' N and in longitude from 119° 30' to 121° 00' E. The populated sections of the city are relatively flat while mountains spur up within city limits and nearby. The highest elevation in the city is located above sea level. Of the total area of Qingdao, 15.5% is highland, while the foothill, plain, and lowland areas constitute 25.1%, 37.8%, and 21.7%, respectively. The city has a -long coastline. Five significant rivers exceeding in length can be found in the region. Climate Qingdao has a temperate, four-season, monsoon-influenced climate that lies in the transition between the humid subtropical (Köppen Cwa) and humid continental (Köppen Dwa) regimes. Qingdao is located in the north temperate monsoon region and has a temperate monsoon climate. Due to the direct regulation of the marine environment, the city is influenced by the southeast monsoon and the currents and water masses from the ocean, so it also has significant maritime climate characteristics. Winters range from cool to cold and windy, but are generally dry, with a January average of . Summer is generally hot and humid, but very hot days are rare, with an August average of . Due to its proximity to the coast and location on a peninsula, compared to most inland areas of China, its spring is delayed by one month, and the annual diurnal temperature variation is only ; conversely, its fall is milder than inland areas in Shandong. The water temperature peaks at about in late August. Thus, swimming is possible for two months on either side. The annual mean temperature is . Extremes since 1951 have ranged from on 16 January 1958 to on 15 July 2002. During the summer months, the beaches of Qingdao are afflicted by massive algal blooms. The decomposing algae release large amounts of hydrogen sulfide gas, which produces an offensive "rotten egg" odor. Sea lettuce blooms, which are partially caused by seaweed farming in Jiangsu Province, led local officials to declare a "large-scale algae disaster" in 2013. Demographics Of the 10 million residents of Qingdao, 6.2 million reside in the Qingdao urban area. Another estimated 5 million live in other cities under Qingdao's jurisdiction. The annual birth rate is calculated around 76,507, with a birth rate of 10.15 per year per thousand, and a death rate of 6.32, both calculated on an annual basis. Living standards are among the highest