By the time Jalaj Jha begins getting ready for work each morning, he already feels drained. The 24-year-old gig worker wakes in a cramped Delhi room with no ventilation except a rattling fan pushing hot air around, facing a 12-hour shift delivering groceries.

“I barely sleep three or four hours in this heat,” Jha said, wiping dust off his motorbike. “I wake up exhausted. It feels like my body is pulling me down.”

It is only 7am, but the temperature is already 30C (86F) - the day’s low. During the day it can top 45C (113F). This week, Delhi recorded its hottest May day in two years and the warmest May night in 14 years.

Rising temperatures are turning cities across south and south-east Asia into places where workers can no longer recover from the heat. A new report by US-based People’s Courage International (PCI), based on research in Delhi, Dhaka, Kathmandu, Jakarta and Quezon City, finds hotter nights plus the urban heat island effect are leaving millions of informal workers exhausted before a new workday even begins.

For delivery riders, construction workers and street vendors living in cramped settlements with little ventilation or unreliable electricity, sleep itself is becoming difficult. The inability to rest and cool down is worsening heat-related illnesses, reducing productivity and pushing already vulnerable workers into deeper economic stress.

The crisis is worsening in south Asia as climate change is predicted to triple the chance of pre-monsoon heatwaves, such as a deadly 15-day one last month. Scientists say night-time temperatures are rising faster than daytime temperatures across much of the region, cutting into the hours people once relied on to recover.

Across Asia, the International Labour Organization estimates more than 70% of the workforce are exposed to excessive heat at some point during their jobs, with informal workers among the most vulnerable. In India, nearly 90% of workers are in the informal economy.

Experts warn cities remain poorly prepared. Some governments, including Delhi’s, have introduced heat action plans, water kiosks, early warning alerts and directions to reschedule outdoor work during peak afternoon heat. But researchers say most responses remain reactive and fail to directly address the needs of workers living and working in extreme heat.

The PCI report, based on interviews with more than 2,200 internal migrant workers across five cities, found nearly eight in 10 said extreme heat was disrupting their livelihoods or households. Workers reported losing wages, spending more on water, medicines and transport, and struggling with headaches, dizziness and fatigue during long outdoor workdays.

“Heat impacts are silent and generally creep up on workers,” said PCI researcher Ameena Kidwai. Workers reported impacts across their lives - at home, work, on their commute, and on their mental health and sense of community.

Ajay Kumar, 32, a roadside vegetable vendor in Gurugram on Delhi’s outskirts, spends hours daily pulling a three-wheeler rickshaw loaded with vegetables through dense traffic after buying produce from a wholesale market 7km away.

“Every day my head spins with the heat. But I have no option but to work for my family,” said Kumar, who has four children.

Researchers describe this growing exhaustion as a “recovery deficit” where workers begin each day already physically depleted. Sleep deprivation is contributing to lower productivity, worsening health, and anxiety.

Kumar, who moved from a village in Bihar four years ago, lives with his wife and children in a cramped room with no ventilation except a rusty fan. He wanted to buy a cooler but cannot afford one.

“I barely make Rp300-400 ($3-4) a day. Most of that goes in feeding my family,” he said. “I keep some water with me and damp my gamcha [scarf]. That helps my head.”

At night, Kumar’s family often sleep on their building’s open terrace because the room becomes unbearably hot.

“But even then, it takes me hours to fall asleep.”