BEIJING - Friday arrived with heavy rain as the first day of China's annual national college entrance examination, the largest of its kind in the world, accompanied by support from armed police, loving families and various types of social assistance.

China has mobilized related state departments to guarantee exam order so to ensure all examinees have a smooth experience of sitting the entrance exam, or gaokao, currently the sole state-sanctioned "bridge" to the nation's institutions of higher learning.

Parents wait in rain outside a test site on the first day of the college entrance examination, in Hangzhou, Zhejiang province, June 7, 2013. [Photo/Xinhua]

In Beijing, all 7,000 of the capital's traffic officers have been dispatched to the roads to maintain traffic order and ensure students get to their exams on time, as torrential rain, thunder and lightning hit most parts of the city, said a spokesman from the Beijing Traffic Management Bureau under the Beijing Municipal Public Security Bureau.

These officers have been prepared to offer immediate assistance to students and their parents, according to the spokesman.

On Friday morning, he said, police escorted two students who faced being late for the test to their exam venues, while many candidates chose to leave home very early to avoid rush hours.

Regions and provinces including Hunan, Anhui, Jiangxi, Shanxi and Guangzhou are set to face heavy rain, which also poses potential risks to electricity supplies.

Hefei, capital city of Central China's Anhui province, has prepared an emergency plan with staff covering shifts round the clock.

Lv Changhui, deputy director of the electricity distribution department of Hefei power supply company, said the firm has prepared 25 teams to work on emergency repairs, with three emergency power cars in operation.