July, the warmest month, is . Rainfall is light in winter and can be heavy in summer, and more than 70% of the annual total occurs from May to September. The annual frost-free period across most of the prefecture lasts from 252 to 300 days, and there are only 1,100 hours of sunshine annually, which is not even 30% of the possible total. Transport The city has highway and railway connections to several major cities and is on the road from Xi'an to the provincial capital of Chengdu as well as the Baocheng Railway running from Baoji in Shaanxi province to Chengdu. Mianyang Nanjiao Airport, which is the second largest airport in Sichuan province, has direct flights to Beijing, Shanghai, Guangzhou, Xi'an, Shenzhen, Kunming, Hangzhou, and so on. G5 Beijing–Kunming Expressway and G93 Chengyu Ring Expressway. Economy Mianyang is one of China's major centres for the electronics industry. It has many well-known research institutions, such as the China Academy of Engineering Physics and China Aerodynamics Research and Development Center. Many large-scale enterprises, such as Changhong Electronics Group Corporation, Sichuan DND Pharmaceutical Co., Ltd., Jiuzhou Electronics Group, Shuangma Cement Group, and Changcheng Special Steel Company also have their home in Mianyang. Mianyang is an important national defence, scientific research, and production base, consisting of 18 institutes including the China Academy of Engineering Physics and the China Aerodynamics Research Institute. Moreover, it houses 50 large- and medium-size enterprises and six science colleges. The provincial government will hand over greater administrative powers of economic management at the provincial-level authority to propel the development of Mianyang. The new economy management authority will pay close attention to the construction of the scientific city. The provincial committee party and government are presently drafting the "Opinions on Propelling China Scientific City Construction" report which is expected to come out soon. Mianyang Hi-Tech Industrial Development Zone Education There are six universities and colleges in the city, and it is well-known as a science and technology centre. The best known of these is Southwest University of Science and Technology, with a campus of 4000 mu (about ). There is a wide-band multimedia campus network, which is connected to the Internet. The student dorm has access to telephone, Internet, and TV. There are over 900,000 copies of books and over 10,000 electronic books in the library. The studying and living facilities are all on the campus. Others: Tianfu College, Southwestern