This story initially appeared on Bulletin of the Atomic Scientists and is a part of the Local weather Desk collaboration.
Through the summer time 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 short-term closure of public places of work and banks. Throughout this era, main reservoirs supplying the Tehran area reached record-low ranges, and water provide techniques got here beneath acute pressure. By early November, the reservoir behind Amir Kabir Dam, a predominant supply of consuming water for Tehran, had dropped to about 8 p.c of its capability. The current disaster displays not solely this summer time’s excessive warmth but additionally a number of consecutive years of decreased precipitation and ongoing drought situations throughout Iran. In consequence, the capital of Iran is now dealing with a possible “Day Zero” when faucets may run dry.
The drought rapidly disrupted Tehran’s city techniques. 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 components of the capital. Amid these escalating pressures, officers warned that the capital metropolis might even need to be evacuated if water provides fail to recuperate. In November, President Masoud Pezeshkian mentioned the capital would need to be moved. These cascading impacts uncovered how susceptible Tehran’s infrastructure, economic system, and communities have change into beneath compounding warmth and drought stress.
These cascading impacts stem from a chronic 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 time. Over the previous 5 years, precipitation throughout this moist interval has remained persistently under the long-term climatological baseline, with the 2024-25 season exhibiting probably the most pronounced and extended deficit throughout the whole wet season. When such extended dryness was adopted by an exceptionally scorching summer time, it amplified hydrological stress throughout the area.
