Most of the displaced in Iraq were forced to flee their homes during successive waves of violence in early 2014 and after ISIS terrorist group offensives in June and August.
Violence continues to force thousands from their homes, and the United Nations Assistance Mission in Iraq said in an update that one of the most affected areas in recent days had been the Kirkuk region.
"More humanitarian actors and greater attention are urgently needed in order to expand the provision of assistance to IDPs (internally displaced people) in Kirkuk," the UN said.
It said snow had begun falling on parts of the Dohuk governorate, the northwestern Kurdish province which hosts the largest number of IDPs in Iraq.
Duhok Governorate is one of the governorates of Iraq, located in the north of the country in the semi-autonomous region of Iraqi Kurdistan. Its capital is the city of Dohuk.
"The lack of proper shelter, thermal insulation of shelters and non-food items will eventually negatively impact the health status of displaced populations during winter," the UN report said.
The Action Against Hunger (ACF) aid organization said displaced people often live in precarious conditions in open spaces, camps and unfinished buildings.
"If the winterization response is not scaled up immediately, we will see both short and long term impacts on the IDP population," the group said in a statement.
The funding gap for this programme alone in the huge crisis response effort needed to assist the millions affected by war in Syria and Iraq stands at $173 million.
Yazidis protest against bad living conditions in Shariya camp
Over ten Yazidis in a camp for the internally displaced were arrested by police on Sunday after a protest against bad living conditions and a lack of food was staged, eyewitnesses said.
Residents in the Shariya camp near Dohuk town complained about conditions after heavy rainfall in recent days.
Some said their tents had been flooded and they had nowhere to live.
Footage shot by the Yazidi Human Rights Organisation showed a large group of people in the camp holding cardboard signs and chanting.
According to eyewitnesses in the camp, police tried to stop the protest and fired warning shots in the air.
Most of the internally displaced in Shariya camp are Yazidis.
The Yazidis are a centuries-old religious minority viewed as apostates by the Iso-called "slamic State" group, which has claimed mass killings of its opponents in Syria and Iraq.
According to United Nations figured, the camp is home to more than 19,000 people.