This story initially appeared on Bulletin of the Atomic Scientists and is a part of the Local weather Desk collaboration.
Throughout the summer season of 2025, Iran skilled an distinctive warmth wave, with daytime temperatures throughout a number of areas, together with Tehran, approaching 50 levels Celsius (122 levels Fahrenheit) and forcing the non permanent closure of public workplaces and banks. Throughout this era, main reservoirs supplying the Tehran area reached record-low ranges, and water provide methods got here underneath acute pressure. By early November, the reservoir behind Amir Kabir Dam, a important supply of ingesting water for Tehran, had dropped to about 8 p.c of its capability. The current disaster displays not solely this summer season’s excessive warmth but additionally a number of consecutive years of lowered precipitation and ongoing drought situations throughout Iran. Consequently, the capital of Iran is now dealing with a possible “Day Zero” when faucets may run dry.
The drought rapidly disrupted Tehran’s city methods. With dry soils and excessive evaporation, rivers and wetlands shrank. Falling reservoir ranges led to disruptions in hydropower technology, and water shortages prompted strict saving measures throughout elements of the capital. Amid these escalating pressures, officers warned that the capital metropolis could even should be evacuated if water provides fail to recuperate. In November, President Masoud Pezeshkian mentioned the capital must be moved. These cascading impacts uncovered how weak Tehran’s infrastructure, financial system, and communities have turn out to be underneath compounding warmth and drought stress.
These cascading impacts stem from a protracted scarcity of precipitation lately (Determine 1a). Precipitation round Tehran usually peaks between December and April, replenishing reservoirs behind dams earlier than the onset of the dry summer season. Over the previous 5 years, precipitation throughout this moist interval has remained constantly beneath the long-term climatological baseline, with the 2024-25 season displaying probably the most pronounced and extended deficit throughout your complete wet season. When such extended dryness was adopted by an exceptionally scorching summer season, it amplified hydrological stress throughout the area.
Seasonal cycle of precipitation averaged over a 1°×1° area centered on Tehran, based mostly on GPM IMERG Remaining Run (V07B) dataset: month-to-month means for 2000/01–2019/20 (black), 2020/21–2024/25 (blue) and 2024/25 (purple).
Illustration: Yeonwoo Choi and Elfatih A.B. Eltahir/Bulletin of the Atomic Scientists
