Large parts of northwestern and northeastern India have shifted towards drier climate zones, while parts of peninsular India have moved towards wetter conditions, a study by the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology, Pune, has found. Researchers analysed rainfall and temperature records from 1951 to 2020.
The paper, titled Identifying the climate zone shifts of Indian meteorological subdivisions: insights from historical records, appeared in the October 2026 issue of Mausam, IMD’s peer-reviewed journal. The authors are Ananya Karmakar, Rajib Chattopadhyay, Pulak Guhathakurta, K S Hosalikar and Mrutyunjay Mohapatra.
Using the Köppen-Geiger classification, the team assessed six climate classes and compared successive 30-year climate periods. It updated the 30-year climatological average every decade, allowing researchers to compare conditions across 1961–1990 and 1991–2020. The classification groups regions according to temperature and precipitation patterns.
The hot arid steppe category has low rainfall and high temperatures. Tropical savannah areas remain warm throughout the year and have a long dry season. Temperate zones have distinct seasonal temperatures. The classification uses long-term averages, so a change reflects a sustained shift in regional climate conditions.
The paper’s abstract reports “a shift to the drier climate zone in North West India and North East India”. In the northwest, areas classified as temperate shifted towards hot arid steppe. In the northeast, areas previously classified as tropical savannah moved into the temperate category.
The researchers estimate that the affected area accounts for nearly 7% of India’s total geographical area. They link the change to rising temperatures and declining rainfall. The paper attributes the pattern to the negative phase of the Victoria Mode and reduced moisture transport.
Hot, dry zone moves east
The hot semi-arid zone has also expanded into parts of Uttar Pradesh, according to reporting on the study. This category describes areas with high temperatures and low rainfall. Its eastward movement means areas beyond western Uttar Pradesh have entered a climate category associated with drier conditions.
Ananya Karmakar, the study’s lead author and an IMD scientist in Pune said that “the clearest change was in the north, where the hot, dry zone has pushed east into Uttar Pradesh”. She said the shift needs monitoring because the state is a major agricultural region.
Peninsular India recorded a different pattern. The hot semi-arid zone declined from 30.3% of the region’s geographical area during 1951–1980 to 16.4% during 1991–2020. Much of this area shifted into the tropical savannah category, which now covers around three-quarters of the peninsula.
The study also found changes along the western coast. Between 1961–1990 and the following climate periods, the tropical monsoon zone extended further across the Konkan, Goa, coastal Karnataka and Kerala. This is the country’s wettest climate category, characterised by heavy seasonal rainfall.
Interior Maharashtra followed a different pattern from much of the peninsula. Marathwada and western Vidarbha, which were largely classified as tropical savannah, shifted into the hot semi-arid category by 1991–2020. Lead author Karmakar attributed this change mainly to increases in daytime and nighttime temperatures.
Climate shifts and farming
The paper warns that the northern climate-zone changes could affect agriculture in the Northern India Agro-Climatic Zone. Changes in temperature and rainfall can alter crop-growing conditions. The researchers say their findings may help improve understanding of climate-zone changes and the IMD’s forecasting system.
Shailender Kumar, an environmentalist and academic councillor at Indira Gandhi National Open University (IGNOU), Delhi, said, “The expansion of the hot, dry zone in northwestern India is significant because the region overlaps with the Indo-Gangetic belt, one of the country’s major agricultural areas.”
He said, “These findings should prompt planning rather than alarm. Cropping calendars, water use and crop choices need to be reviewed against updated regional climate data.”
On the possible role of ocean patterns, Kumar said, “The relationship between rainfall changes and ocean patterns, including the North Pacific’s Victoria Mode, needs further investigation before these changes can be attributed to a single factor.”
The researchers examined the role of ocean-atmosphere patterns in the observed changes. The paper links the northern shift to the negative phase of the Victoria Mode, which it says reduced moisture transport and contributed to divergence over the northern Indo-Gangetic Plain. This is the physical mechanism proposed by the researchers.
The study compares climate averages over 30-year periods, so its results describe broad regional classifications, not the weather in every district or year. The eastward movement into Uttar Pradesh and the contrasting changes across peninsular India show how temperature and rainfall patterns have changed across different parts of the country.
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