Hot February, cool May: what the first half of 2025 says about India’s shifting weather

 It’s not just rising temperatures—moisture, unpredictability, and urbanisation are reshaping how India experiences heat.

Vaishnavi Chandrashekhar

One of Sanskrit poet Kalidasa’s most famous poems celebrates the shifting moods of the Indian calendar year in six cantos titled The Pageant of Seasons. Were the fifth-century poet writing today, he might have called this year: A Confusion of Seasons.

Take the past six months. Winter ended early, skipping spring and jumping into summer-like heatwaves that made February the hottest on record. Then, May threw a curveball with an early monsoon arrival, which brought record rains to Mumbai, Delhi, and Bengaluru. Now, a recent regional forecast suggests the monsoon months ahead will see warmer nights than usual.

There is an emerging pattern here: due to global warming as well as land-use change and urbanisation, heat is no longer about summer nor is it defined solely by temperature.

To understand this trend better, it’s worth looking closely at the past few months of weather in the big cities of Mumbai and Delhi. In February, the capital saw above average day temperatures and the warmest night on record for the month since 1951, while Mumbai saw temperatures reach 38.7C, or 5.9C over the normal. The city as well as parts of coastal Maharashtra received heatwave warnings. (For Kalidasa, this month would have been, at most, early spring.)

May is usually the peak of summer, but this year the Met department had to issue rain alerts instead as the monsoon arrived in Mumbai 16 days earlier than usual---the earliest since 1956. It was also Mumbai island’s wettest May on record, chalking up 504mm of rainfall in the Colaba station—much of it in a few heavy inundations that took the city by surprise. The rain was due to regional weather systems that lowered temperatures in large parts of the country In Delhi, too, much of May turned out to be cooler than April and broke local rain records.

But the chill didn’t last. In June, the monsoon hit pause and higher temperatures returned, making north Indian cities like Delhi unusually muggy.

The impact of these weather swings is considerable. February’s early heat threatened Punjab’s wheat crop. May’s heavy downpours destroyed more than 4000 hectares of cropland in Marathwada—the arid district received 1000% more rain than it usually does. Meanwhile, the cities were hit by floods. May is the season that Mumbai finishes up its rain-proofing measures—from repairing buildings and desilting nullahs to trimming tree branches and preparing dewatering pumps. So, the city agencies were caught off guard: the May deluge led to waterlogging and disrupted transport systems, unexpected tree falls, and house collapses. There were also health fallouts: a surge in conjunctivitis and other viruses due to the fluctuating temperatures and high humidity, doctors said.

The mention of humidity is telling. An important shift in recent years is that heat is no longer seen as just about how high the air temperature climbs--but about how unbearable it feels. And that sensation has a lot to do with the moisture in the air. Scientists are increasingly looking at a measure known as the Wet Bulb Globe Temperature (WGBT), which combines temperature, humidity and other conditions to understand “moist heat” levels. This is important because humans rely on sweating as a mechanism for cooling down when body temperatures exceed 37C—but the moister the air, the less we can sweat, increasing heat stress.

Studies show that humidity is rising across India, especially in the north. Last year, a study led by scientists at Cornell University using WGBT measures found that the area exposed to extreme levels of humid heat during monsoons increased by almost 43 million sq-km—representing 670 million people—between 1951-2020. The Indo-Gangetic plain and eastern coast were most vulnerable to wet-bulb temperatures over 38C, the researchers found. Another study, released just last month from the Council on Environment, Energy and Water (CEEW), highlighted a similar trend. It found that summer humidity in north India rose in the last decade from 30-40% on average to 40-50%. Cities like Delhi, Chandigarh, Jaipur, and Lucknow have seen a 6-9% rise in humidity levels. Even early mornings now feel hotter due to humid conditions, the study noted.

Global warming is partly responsible for the rise in humidity—for every one-degree Celsius rise in temperature, the air can hold an average of 7% more water vapour. Increased irrigation is also thought to play a role. Short-term weather systems are also a factor. This year’s early rains, for instance, were partly driven by what are known as Western Disturbances. These are storms that originate in the Mediterranean and bring rainfall to the northwestern subcontinent in winter, but this year they extended into May, leading to unseasonal rains. (Global warming may be increasing the frequency of these disturbances.)

Whatever the driver, the early rains helped raise summer humidity in New Delhi. The city is known for its dry frying-pan heat but felt more like a sauna this summer, by some accounts. The city recorded 74% relative humidity on one day—the levels more often experienced by coastal Mumbai. Thanks to the Indian Met Department’s new ‘heat index’, which combines air temperature and humidity levels, we are beginning to understand the “real feel” of heat. In New Delhi, newspapers noted while the temperature on June 12 was 43.9C—four degrees above normal and the hottest day of the summer—the heat index or real feel was 54.4C due to high humidity.

What does all this mean? For people reading this column on the internet and in English, perhaps it doesn’t mean much—we can escape into air conditioning if we need to. But those who work outdoors—on farms, construction sites, and streets—or live in tin-roofed bastis with poor ventilation and drainage will be badly affected, and need help to cope. For the city and country at large, this matters: without interventions, unseasonal heat and extreme rains will hit labour productivity and crop yields and, ultimately, the nation’s wealth and well-being.

State responses so far have largely focused on short-term or emergency coping mechanisms. Cities have improved heat alerts, adjusted school timings, and promoted ‘cool roofs’ covered in solar reflective paint. These are important steps—but they’re not enough.

The recent CEEW study offers us some insights to what more is needed.  For the analysis, researchers created a heat risk index for 734 districts of India, using decades of climate data as well as trends in population, land use, and socioeconomic conditions. They found that central Maharashtra, Vidarbha, and Andhra Pradesh are sensitive to heat stress due to a large outdoor working force engaged in agriculture. In Punjab, West Bengal, Kerala, Karnataka, and Tamil Nadu, they found vulnerability linked to high prevalence of non-communicable diseases such as anaemia, hypertension, and diabetes.

Meanwhile, Mumbai, Delhi, and much of the Indo-Gangetic plain faced the highest exposure to heat risk due to high population, dense built-up areas, and socio-economic conditions. Urbanisation plays an important role in raising minimum temperatures because concrete prevents heat from dissipating at night—and human bodies from cooling down. Indeed, the study found very warm nights have increased faster than very hot days in the past decade, with Mumbai seeing 15 additional very warm nights per summer and Delhi six. By contrast, districts in Odisha with more green cover and water bodies are better able to cope, the study found, despite other vulnerabilities.

Their conclusion: “States, districts, and cities should move beyond a narrow focus on daytime temperatures while planning for heat risk and incorporate additional dimensions of warm nights, humidity, demographic patterns, and health vulnerabilities,” into the second generation of Heat Action Plans. Increasing green cover and expanding access to electricity, healthcare, and drinking water are also key to mitigating heat stress as well as unseasonal rains and floods, they added.

Such longer-term measures might not turn the tumultuous weather wrought by global warming back into Kalidasa’s “pageant of seasons”—but they will make them more manageable. 

Earth Shifts, a monthly column on The Migration Story, will analyse the impact of global green goals amid mounting climate uncertainties on lives and livelihoods. 

Vaishnavi Chandrashekhar is an environment and science journalist based in Mumbai.