The UN High Commissioner for Refugees said that as of Thursday, 612,134 Syrians had either been registered as refugees in neighbouring countries or were in the process of being registered, up from 509,550 announced on December 11.
"This is a sharp increase," UNHCR spokesman Adrian Edwards told reporters in Geneva, adding that despite winter preparation, "many refugees in both camp and non-camp situations are facing particularly cold and damp conditions."
UNHCR said it had registered nearly 176,600 refugees in Jordan, but stressed that the Jordanian government put the total number at around 280,000.
Edwards said the first week of 2013 had "seen a surge in new arrivals" to Jordan, where more than 1,100 Syrians cross the border every day.
"Many of those arriving have been barefoot, with their clothing soaked and covered in mud and snow," he said.
Nearly 200,000 were registered in Lebanon, more than 153,000 in Turkey, 69,300 in Egypt, 69,000 in Iraq, 13,000 in Egypt and over 5,000 in North Africa.
The announcement came as UN-Arab League peace envoy Lakhdar Brahimi was meeting with top US and Russian officials in Geneva in a fresh bid to find a way out of the nearly 22-month long Syria conflict, which the UN estimates has left over 60,000 dead.
The UN has said it expects the number of Syrian refugees in neighbouring countries will rise to 1.1 million by next June if the war continues.