NEW DELHI — Across a wide swath of the Indian subcontinent, scorching temperatures have damaged harvests. People are suffering from heat stroke. And the lights are flickering in some cities amid surging demand for air-conditioning.
Now, the heat wave that has been pummeling India and Pakistan for weeks is expected to intensify over the weekend. In some hard-hit areas, it may be weeks before the region’s annual monsoon sweeps in to provide relief.
Heat-related watches were in effect on Thursday afternoon for all but a few of India’s 28 states, encompassing hundreds of millions of people and most of the country’s major cities. An alert — one notch up in severity — was in effect for the northwestern state of Rajasthan on Thursday, and would come into effect for other central and western states starting Saturday.
The heat wave poses health and logistical challenges for manual laborers, farmers, firefighters, power engineers, government officials and others, particularly in areas where air-conditioning is scarce.
“Our condition is not good,” said Sawadaram Bose, 48, a cumin and wheat farmer in Rajasthan, where temperatures climbed to 112 degrees Fahrenheit this week. He and his family are only leaving the house before 11 a.m. or after 5 p.m., he said, and never without a water bottle or head and face coverings.
The temperatures are well above normal.
The subcontinent’s scorching weather is a reminder of what lies in store for other countries in an era of climate change. Climate scientists say that heat waves around the world are growing more frequent, more dangerous and lasting longer. They are certain that global warming has made heat waves worse because the baseline temperatures from which they begin are higher than they were decades ago.
“Extreme heat is obviously one of the hallmarks of our changing climate,” said Clare Nullis, an official at the World Meteorological Organization, a United Nations agency that certifies weather records at the international level.
It is too early to say whether the current temperatures in India or Pakistan will lead to any new national-level weather records, she added.
In India, where forecasters said that March was the hottest month the country has witnessed in over a century, the National Weather Forecasting Center said this week that temperatures in some states were 10 degrees Fahrenheit or more above normal in some areas.
The heat-related watches in parts of southern and eastern India, where rain was in the forecast, were expected to end within a day or two, the authorities said. But in a diagonal band stretching from Rajasthan in the northwest to Andhra Pradesh in the southeast, the watches were expected to persist or be elevated into heat alerts through Monday.
The forecast looked similar in most of neighboring Pakistan, where government forecasters said this week that a high pressure system would likely keep temperatures above normal through Monday.
Pakistan’s Meteorological Department also warned that in regions dotted with glaciers, the heat could lead to so-called outburst floods, in which water spills from glacial lakes into populated areas. In 2013, an outburst flood in the northern Indian state of Uttarakhand led to flooding that destroyed villages and killed several thousand people.
In both countries, the forecasts cited only temperature, not the heat index — a measure that combines temperature and humidity and tends to give a more accurate portrait of what extreme weather feels like.
Fusaram Bishnoi, a doctor in Barmer, an area ofRajasthan that has recorded some of India’s highest temperatures this week, said he had seen a surge of patients arriving with heat-related illnesses in recent days. That includes not only heat stroke, he said, but also food-borne illnesses linked to the consumption of food that spoiled in the heat.
“We tell people not to venture out during the day and to drink more, and more water,” Dr. Bishnoi said.
‘Everything is ready to burn.’
The extreme heat poses a problem for agriculture, a primary source of income for hundreds of millions of people across the subcontinent. In India, wheat farmers have been saying for weeks that high temperatures were damaging their yields. The Indira Gandhi Memorial Tulip garden closed a week early this spring because many bulbs had flowered and then died before an annual monthlong exhibition had run its course.
Mr. Bose, the farmer, who lives in the Barmer district of Rajasthan, said that about 15 to 20 percent of the local wheat crop, as well as half the cumin crop, had already been lost because of unseasonably hot weather and changes in wind flow. It does not help, he added, that the current heat wave has made it harder to work outdoors.
“No work during the day in the fields,” he said.
The heat wave is also straining basic municipal services. In India, more than 10 states, including the one that includes the city of Mumbai, have faced power shortages in recent days. That is partly a function of the heat, but also of a national shortage of coal, a fuel that accounts for about three-quarters of the country’s power supply.
In New Delhi this week, there has been a rash of landfill fires that officials said were caused by spontaneous combustion. Prime Minister Narendra Modi of India said on Wednesday that the extreme heat was raising the risk that more fires would occur in the capital, and beyond.
Calls to fire departments in New Delhi typically rise at this time of year, but an increase in recent months — from 60 to 70 calls per day to more than 150 per day — has been larger than usual, said Atul Garg, the director of fire services in New Delhi.
“Everything is ready to burn,” he said.
Hari Kumar reported from New Delhi and Mike Ives from Seoul.