It’s been less than five minutes since Médécins Sans Frontières (MSF) health promotion team stepped inside the tent of a Syrian refugee family, and already pearls of perspiration are trickling down their faces.

The last few weeks have brought unprecedented temperatures to much of the Middle East. In Lebanon’s Bekaa Valley, home to at least 410,000 refugees, temperatures have reached as high as 42 degrees. The heat isn’t just bringing discomfort; it’s bringing sickness.

Many Syrians in the Bekaa live in unfinished buildings or in one of over 900 informal tented settlements (ITS) haphazardly erected in fields or along the roadside. The flimsy plastic sheeting that make up the walls and roofs of the ITS offers little respite from the blazing sun. Dust blows in and out of these homes, and the air is thick with humidity and flies. Access to clean water is limited and sewage often leaks into the areas surrounding the tents, where children play.

At MSF’s four clinics across the Bekaa, more than half of the patients currently seeking treatment are suffering illnesses resulting from the hot weather. “In summer, we always see a lot of respiratory tract infections, gastro-intestinal problems, such as diarrhea, and dermatological problems,“ says Dr. Bilal Qassem, a doctor at MSF’s clinic in Baalbek. “These morbidities are all directly linked to the poor living conditions our patients endure. We’ve seen a 20% increase in the usual summer morbidities compared to last year, possibly because of the recent heat wave.”

In June and July, upper and lower respiratory infections counted for over 42% of the diseases treated by MSF in the Bekaa. In July, watery diarrhea and gastro-intestinal problems amounted to 23% of the diseases treated.

With limited access to clean water and overcrowded tents, skin diseases like scabies are also common. As the health promotion team prepares to leave the ITS, a man rushes over to show them red welts covering his belly and arms, the telltale sign of scabies. “Because of the cramped living conditions, when one person gets sick, everybody else gets sick too,” says Dr. Wael Harb, head of MSF's medical activities in the Bekaa.

“We provide medicine and our health promotion teams explain how to reduce the spread of infection, but we can’t change the underlying cause of these problems, which are poor hygiene and precarious living conditions,” he adds.

As the seasons change, so too will the challenges for refugees. “The summer is hard, yes, but winter is much, much worse,” says Leila*, a Syrian mother of five living in an ITS near Majdal Anjar. “In winter you can’t keep your children warm, the plastic sheeting always rips and you have to spend your days shoveling snow off the roof.”

*Indicates her name has been withheld