HYDERABAD: For years, Hyderabad’s weather followed a familiar pattern. Summers were hot, the monsoon brought most of the year’s rain and winters remained relatively dry. However, a 42-year analysis of meteorological data by researchers from the Meteorological Centre, Hyderabad, published in the Madras Agricultural Journal, suggests that this pattern is gradually changing.
Analysing rainfall, maximum and minimum temperatures, and evapotranspiration (ETo) data from 1981 to 2022, the study found a gradual decline in monsoon rainfall alongside steadily rising temperatures, trends that are raising concerns about water security, urban planning and climate resilience in the city.
The findings are particularly significant because Hyderabad depends heavily on the monsoon. On average, the city receives 736.5 mm of rainfall every year, and nearly 80% of it arrives during the southwest monsoon between June and September. Yet the data shows that these crucial seasonal rains have been declining, signalling a shift in long-established weather patterns.
Rainfall, meanwhile, is becoming increasingly unpredictable. Monthly variation ranged from 43.5% in August to as high as 269.4% in February, highlighting uneven rainfall distribution. August remained the wettest month with an average rainfall of 161.5 mm, followed by July (155.3 mm) and September (133.1 mm), while December and February received just 3.5 mm and 3.9 mm, respectively.
The biggest fluctuations were recorded outside the monsoon season. Pre-monsoon, post-monsoon and winter rainfall showed high variability, with November indicating a greater likelihood of extreme rainfall events. Researchers noted that rainfall beyond the core monsoon months is becoming increasingly erratic, with intense downpours often followed by prolonged dry spells.
Statistical analyses, including the Mann-Kendall test and Innovative Trend Analysis, also confirmed a gradual decline in monsoon rainfall.
While rainfall is becoming less dependable, temperatures are steadily rising. Across the 42 years, maximum temperatures increased at a Sen’s slope of 0.012°C, while minimum temperatures rose at a slightly faster rate of 0.02°C, reflecting broader warming trends associated with climate change.
May remained the hottest month with an average maximum temperature of 42.7°C, with temperatures touching 45°C in some years. April averaged 42°C and March 40.1°C, while cloud cover and rainfall kept August and September relatively cooler at 31.7°C and 31.3°C, respectively. Night-time temperatures also showed a gradual increase, with average minimum temperatures ranging from 11.2°C in December to 23°C in May, indicating warmer nights across the city.
The researchers also examined evapotranspiration (ETo), a key measure of atmospheric demand for water. May recorded the highest average ETo at 289.4 mm due to intense summer heat, while September recorded the lowest at 109.8 mm during the monsoon. Although seasonal ETo showed a declining trend of -0.16, month-to-month variations remained significant, with November recording the highest variability at 20.5% and February the lowest at 7.1%.
Taken together, the findings suggest Hyderabad may be heading towards a future of hotter temperatures and less predictable rainfall. Researchers warn that declining rainfall, rising temperatures and changing evapotranspiration patterns could affect groundwater recharge, reservoir storage and agricultural productivity, while increasing the risk of heat stress, droughts and water shortages.
The changes may be gradual, but the message is clear: for a city that relies heavily on the monsoon, understanding and preparing for these long-term shifts could be crucial in the years ahead.
