Haryana’s dairy farmers have watched their buffalo herds struggle through July and August for years. Now they know why. A new study in Scientific Reports pins the blame on a specific climatic double punch: temperatures above 38°C and humidity over 70%.
The research combed through 15 years of data — 2004 to 2019 — across 1,148 villages in the state. That is the trans-Gangetic plains, the high-production tract that helps make India the world’s largest milk producer.
The numbers are enormous: 35.56 million buffaloes, 4.66 million cross-bred cattle, 2.86 million indigenous cattle. The scientists matched each animal’s milk yield against yearly minimum, maximum, and mean temperatures, heavy rainfall, the temperature-humidity index, and evapotranspiration. The finding is blunt.
Extreme heat and monsoon humidity together create physiological strain that “significantly reduce milk production.” Winter temperatures? Negligible effect.
The problem concentrates in July and August, when summer heat meets the monsoon. Buffaloes take the worst of it. They dominate Haryana’s dairy herds.
That makes the state’s milk supply especially vulnerable to climate shifts. Evapotranspiration in May and June also matters, the study flagged. So does solar radiation, ambient temperature, and vapour pressure.
The climate assessments used all of these to understand what is hitting the herds. Haryana sits in the northwest, part of the trans-Gangetic plains that are one of India’s biggest milk sources.
A drop in yield here does not just hit farmers. It reaches every consumer who buys milk daily. The study’s authors say the heat-humidity combination acutely undermines dairy production across the global south.
India is the world’s largest milk producer. The trans-Gangetic plains are one of its biggest sources.
So a climate-driven drop in yield here matters beyond Haryana. But on the ground, it is local. Farmers in those 1,148 villages see it in their pails every monsoon.
The science now confirms what they have suspected: the hot, wet months are squeezing their livelihoods. The study examined over a decade of data. That is a long enough window to see a trend, not a fluke.
The pattern is clear: when the temperature climbs past 38°C and the air turns thick with humidity, production nosedives. India’s dairy industry is built on buffalo milk.
Buffaloes are particularly vulnerable to heat stress. That is a structural weakness the study exposes. The researchers did not just look at temperature.
They looked at the temperature-humidity index, which combines both factors into a single measure of heat stress. They looked at evapotranspiration, which measures how much water evaporates from soil and transpires from plants.
All of it points the same direction. Haryana’s dairy farmers face a future where the monsoon, once a relief, becomes a threat. The study gives them a diagnosis.
It does not give them a cure.
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