‘We have nothing to keep us warm and dry.’ Winter adds to the misery in Gaza.

At night, amid heavy rains and dropping temperatures, Heba and Ehab Ahmad held their two youngest children tightly, relying on their body heat and a thin blanket to keep them warm as water and gusts of wind blew through the holes in their makeshift tent.

“We have nothing to keep us warm and dry,” said Ms. Ahmad, 36. “We are living in conditions that I could have never in my entire life imagined were possible.”

The Ahmad family is among the 1.9 million Gazans who the United Nations says have been displaced since Israel began its relentless bombing campaign and expanded ground operation in retaliation for the Oct. 7 Hamas-led attacks on Israel.

They came to Gaza’s southern Al-Mawasi neighborhood three weeks ago, just as winter crept in. The family of seven took shelter in a small, flimsy tent that they built using overpriced nylon sheets and a few wooden planks, said Mr. Ahmad, 45. They share it with 16 other relatives, he added.

“It’s not even a proper tent,” he said, jokingly. “Those who are staying in real tents are the bourgeois in Gaza.”

During the daytime, Mr. Ahmad said, he and his eldest sons attempt to find firewood and cardboard to keep a small fire going, which they use to cook and stay warm. “I’m speaking to you while the smoke from the fire is blinding me,” Mr. Ahmad said in a phone interview on Sunday. In the background, someone could be heard coughing uncontrollably. “The smoke is also hurting our lungs,” he added.

The U.N. and other rights groups have in recent days expressed growing concerns about the further spread of waterborne diseases like cholera and chronic diarrhea in Gaza, with the lack of clean water and unsanitary conditions. Children have been the most severely affected by the increasing rates of infectious disease, according to UNICEF.

Mr. and Ms. Ahmad’s only daughter and youngest child, Jana, 9, had been suffering from severe abdominal pain for nearly two weeks, possibly from extreme dehydration, Mr. Ahmad said. He said he has not been able to take her to a hospital or clinic because the few medical centers that remain functional are completely overwhelmed and hard to reach on foot.

“She’s been screaming in pain, and all we can do is give her some of the rainwater to drink,” Mr. Ahmad said.

The weather was warm when the Ahmads and their five children first fled their home in the northeastern city of Beit Hanoun during the early days of the war. Like many others, Ms. Ahmad said, they did not anticipate being gone for this long and had fled with only some documents and the summer clothes they had on their backs.

“I have been going to look for warm clothes at secondhand street markets,” Mr. Ahmad said, “but they are selling them for insane prices that I can’t afford.”

“For 23 days, we have been trying to find blankets and mattresses,” Mr. Ahmad said. “We have been sleeping on a thin sheet and shaping the sand into a sort of pillow to rest our heads.”

This week, the Integrated Food Security Phase Classification, an international partnership of aid organizations, classified Gaza’s entire population as in crisis in terms of access to food.

Like many other displaced families, the Ahmads, who have moved four times since the start of the war, have struggled to find food and water. They have been eating whatever they could forage, mostly wild leafy greens, Mr. Ahmad said. He added that no aid had reached them so far. Distribution of aid has been complicated by fuel shortages, continued airstrikes and a multitude of other logistical challenges.

There is a silver lining to the rainy weather, though — a short break from the family’s daily struggle to find water.

They placed a bucket outside their tent to collect rainwater, which they used to cook and wash themselves and their clothes.

“It is still contaminated water,” Mr. Ahmad said, “but we have no other alternative. We need to adapt.”

Ameera Harouda contributed reporting from Doha, Qatar.