Leaders of the Hong Kong Federation of Students will decide in the next week whether to call on protesters to pull up stakes from camps straddling some of the Chinese-controlled city's main thoroughfares which have created havoc for transport and business and tried residents' patience.

About 20 protesters dressed in thick jackets waited out cooler temperatures on Friday in the main Admiralty protest site, next to the Central business district, while tents were covered in plastic bags and tin foil for insulation and protection from the rain.

Student Keith Ng, 17, who has his first exam on Monday, reflected the overall mood, nursing a heavy cold.

"I am in the first aid team here, so I have to stay till the end," he said. "But for the other protesters, I think they will retreat as morale is very low now."

Hong Kong, a former British colony, returned to Chinese Communist Party rule in 1997 under a "one country, two systems" formula that gives it some autonomy from the mainland and a promise of eventual universal suffrage.

Beijing has allowed a free vote in 2017, but insists on screening any candidates for city leader first.

Chief Executive C.Y. Leung told the Hong Kong Economic Times that protesters still occupying the streets were the more radical ones, and this was why action should be taken to clear the camp sites.

Police are expected to clear the streets of the Admiralty area from Wednesday, media said, and many students like Timothy Sun, 18, who was arrested on Sunday, said he would leave.

"I can't afford to be arrested for a second time," Sun, who is on a gap year, said.

Benny Tai, one of the founders of the "Occupy Central" movement, reiterated calls for students to leave and pondered where the disobedience movement could go next.

"Blocking government may be even more powerful than blocking roads," he wrote in the International New York Times.

"Refusal to pay taxes, delaying rent payments by tenants in public housing ... along with other such acts of non cooperation, could make governing more inconvenient."

Despite the expected police clear-out and a retreat by the main student federation, some were likely to stay put.

"After more than two months here, many see this place as their home," said Louis Tong, 20. "They won't leave because we haven't achieved anything."

But Tai said much had been achieved by the so-called Umbrella Movement, despite the fact that the government had not met its demands for a free vote.

"The Umbrella Movement has awakened the democratic aspirations of a whole generation of Hong Kong people," he wrote. "In this sense, we have achieved much more than we could have hoped for."