Heavy rains over the past week have compounded the already dire living conditions of the hundreds of thousands of displaced Palestinians in the Gaza Strip, UN agencies say.
Unicef spokesman Jonathan Crickx told the BBC that the weather overnight had been horrendous, with the rain so intense that he had seen up to 15cm (6in) of water on the ground near his office.
He said he was extremely concerned that children living in tents and makeshift shelters in wet clothing would succumb to hypothermia and other illnesses.
Gaza's Hamas-run health ministry has said one baby has died from hypothermia and at least 11 other people have died in building collapses caused by the severe weather.
UN agencies have stepped up deliveries of tents, blankets and clothes since the Gaza ceasefire began nine weeks ago, but they have said there is still not enough aid getting in.
The UN and its partners estimate that almost 55,000 families have so far been affected by the rains, with their belongings and shelters damaged or destroyed.
More than 40 designated emergency shelters were severely flooded following downpours on Monday and Tuesday, forcing many people to relocate again.
Last night was really horrendous for the families. The heavy rains were so intense that we could see from our office and guest house 10cm, 15cm (4-6in) of water at some point. And the winds were so strong, Jonathan Crickx, chief of communications for Unicef State of Palestine, told the BBC's Today programme on Wednesday.
He noted that most of the estimated one million people living in tents and makeshift shelters had been displaced many times during the two years of war between Israel and Hamas, and that they had no or very few changes of clothes.
Mr. Crickx said Unicef had been able to bring in more aid during the ceasefire to help children cope with the harsh winter conditions, including 250,000 winter clothing kits, 600,000 blankets and 7,000 tents, but that it was not enough.
The health ministry reported that a two-week-old boy named Mohammed Abu al-Khair had succumbed to hypothermia, and additional fatalities were documented due to building collapses amidst the harsh weather.
We call on the world to solve our problems and rebuild the territory so that people can have homes instead of being displaced and living in the streets, said a relative of a casualty from a collapsed building.
The UN stresses the urgent need for sustained humanitarian assistance to address immediate and long-term needs, including food, shelter, and vital infrastructure repairs.
