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 to relocate again.
Crickx said that many people were trying with buckets to remove water and that, with night temperatures dropping to around 7C (45F), the risk of sickness was dangerously high for children.
Gaza's health ministry reported a two-week-old boy had died of hypothermia and additional casualties due to collapsing shelters further heightened concerns about safety.
The International Committee of the Red Cross urged for increased humanitarian assistance to help cope with urgent needs for food, shelter, and infrastructure repair.
Despite claims to the contrary, the Israeli military asserted that humanitarian aid continues to flow into Gaza, but according to reports, the scale of assistance is still insufficient, particularly in light of the escalating weather crisis.
