Iran Climate – September 2026 Update
Top 5 Cities: Tehran, Mashhad, Isfahan, Karaj, and Shiraz
Summary
Iran experienced its hottest September since records began in 1940, with sweltering late-season heat crowning an extraordinary summer of regional temperature records. Across the country, extreme conditions pushed localised temperatures past 50°C in southern provinces, exacerbating severe hydrological stress and chronic reservoir shortages. The exceptional warmth coincided with a strong El Niño in the tropical Pacific, which is forecast to peak at Very Strong strength during Sep-Nov. Looking forward, seasonal models indicate elevated warmth will persist while El Niño shifts probability toward autumn rainfall.
This month in numbers
The nation recorded an average temperature of 27.26°C in September, sitting 3.2°C above the 1961-1990 baseline. This was the 1st warmest September in 87 years of records, surpassing all previous highs for the month. The three-month period from July to September also set an all-time record at 29.74°C (+2.7°C anomaly). Globally, land temperatures reached their 2nd highest September level on record with an anomaly of +1.9°C.
What changed
The relentless heat across July to September locked in the region's warmest late-summer quarter on record. Compared with regional peers, Iran recorded the highest temperature anomaly in the Asia group for the month, running 1.41°C warmer than the continental average. This warmth builds upon long-term trends that have raised Iran's average temperature by 2.26°C relative to pre-1990 baselines.
What’s driving change?
The anomalous warmth is backed by , where parched soils from multi-year rainfall deficits lose the capacity to cool through evaporation, allowing solar energy to directly heat the lower atmosphere. Stalled high-pressure further trapped warm air masses across the Iranian plateau. Globally, the climate background is influenced by a strong El Niño, which continues to intensify in the Pacific as tracked at ENSO.
Looking ahead
Seasonal models project that El Niño conditions will remain 100% likely through winter, tilting the odds toward above-average autumn precipitation across Iran alongside sustained warm temperatures.
Generated by Gemini from climate data and web sources
At a Glance
Temperature – Average
Long-Term Trends
Climate Insights – Iran
Precipitation, Sunshine, Frost and Snow are converted to standard deviations from their own average so they can share an axis with Temperature anomalies.
Climate History
36 of 36 events
Data: Our World in Data / NOAA (precipitation: GPCC (DWD); frost: World Bank CCKP).
Heatwave Days – Iran
Warm Spell Duration Index (WSDI) - days in a 6+ day run above the local 90th-percentile temperature for that time of year.
Data: World Bank Climate Change Knowledge Portal (ERA5-derived). Refreshed roughly 1-2x/year, ~7-8 months behind present.
Climate Map – Global
Source: Copernicus ERA5 (countries) · NOAA Climate at a Glance (continents, US states & climate regions) · Met Office (UK) · GPCC (rainfall, snow) · World Bank CCKP (frost). Anomalies are vs the 1961–1990 baseline. See methodology.
Year-on-Year Trends
The 4byo Climate Helix – Iran
Data: Our World in Data / NOAA (precipitation: GPCC (DWD); frost: World Bank CCKP).
Monthly Temperature – Iran
Background lines show the last 40 years (plus the record year and its opposite, wherever they fall).
Data: Our World in Data / NOAA (precipitation: GPCC (DWD); frost: World Bank CCKP).
Records – Iran
Our World in Data / NOAA (precipitation: GPCC (DWD); frost: World Bank CCKP) - Anomalies vs 1901-2000 mean
Typical Climate – Iran
Köppen BSh · AridIran has a arid climate (Köppen BSh: Hot steppe), with both a warm/cold cycle and a wet/dry cycle through the year. July is typically the warmest month, averaging 31.2°C, while January is the coldest at 6.5°C. Annual precipitation averages around 223mm (about 9mm of it as snow), concentrated mostly in the wet season.
Monthly climate normals (2016–2025) - bar colour and height show average temperature, the shaded area shows average monthly rain, with snow (water-equivalent) shown separately.
Data: Our World in Data / NOAA (precipitation: GPCC (DWD); frost: World Bank CCKP).
Shifting Seasons
Warm/cold + wet/dryKöppen BSk · AridIran has both a clear warm/cold cycle (±12.5°C) and a wet/dry cycle (10× wet:dry ratio). Both sides of the annual rhythm are shown below.
Monthly precipitation climatology. A “wet month” exceeds the baseline monthly mean (dashed gold line). Biggest month-to-month shift: Dec (-8 mm, -22%).
Data: Our World in Data / NOAA (precipitation: GPCC (DWD); frost: World Bank CCKP).
Extreme Weather
Alerts & Disasters - Iran
GDACS alerts in Iran right now, graded Red (Major), Orange (Severe) or Green (Moderate), and the long-term record of weather and climate disasters.
Live Alerts
Alerts, Last 12 Months
Major
0
None since 2021
Severe
0
None since 2021
Moderate
9
Weather Disasters in 2024 - Latest Complete Year
Disasters
4
3.4 a year, 2015-2024
Deaths
44
42 a year, 2015-2024
Weather Disasters, 2015-2024
Most Frequent
Flood
25 of 34 disasters
Deadliest
Flood
390 of 424 deaths
Disasters: EM-DAT, CRED / UCLouvain, via Our World in Data - 10+ deaths, 100+ people affected, or a declared emergency or call for international help. Alerts: GDACS.
Climate Drivers
Climate Drivers - Iran
The natural climate patterns that measurably shape seasonal temperature or rainfall in Iran, from this site’s own data since 1950 - long-term trends removed, and ENSO’s share taken out before scoring the others, so each is credited only for what it adds.
The tropical Pacific’s warm and cool swings - the biggest natural driver of year-to-year climate.
Now: El Niño (strong) · RONI +1.7°C (Jul-Sep 2026)
Forecast - 100% very strong at peak, Sep-Nov, then neutral by Apr-Jun 2027 (NOAA). La Niña from Oct 2027 in SNU’s AI model.
Strongest in Aug-Oct rainfall: El Niño tends to bring wetter conditions here, La Niña the reverse (about 31% of year-to-year variation).
ENSO TrackerSteers the North Atlantic storm track - Europe's winters especially.
Now: positive · +0.37 (30-day mean to 2026-10-13)
Strongest in Jan-Mar temperature: a positive NAO tends to bring cooler conditions here, a negative NAO the reverse (about 27% of year-to-year variation). Also Sep-Nov temperature (positive NAO: cooler).
NAO TrackerHow readily Arctic air spills south - tied to the polar vortex.
Now: positive · +1.05 (30-day mean to 2026-10-13)
Strongest in Jan-Mar temperature: a positive AO tends to bring cooler conditions here, a negative AO the reverse (about 25% of year-to-year variation).
Polar Vortex / AOEmissions & Energy
Explore
Explore Climate Data
Data Sources
Data Sources for Iran
Every figure on this page is sourced from official, openly published climate datasets. Anomalies are calculated against the 1961–1990 baseline (temperature) and 1991–2020 (rainfall, sunshine, frost) - see the Methodology & Sources page for the complete dataset list and update calendar.
Country-level temperature anomaly, sourced from Copernicus ERA5 and Hadley HadCRUT5.
Annual country and global CO₂ emissions, from the Global Carbon Project.
Monthly rainfall - Global Precipitation Climatology Centre (DWD) preferred, World Bank CCKP/CRU TS fallback where GPCC lacks direct coverage.
Frost Days and Heatwave Days (Warm Spell Duration Index), ERA5-derived. World Bank Climate Change Knowledge Portal.
Monthly snow water-equivalent, Global Precipitation Climatology Centre (DWD).
Live and archived alerts for cyclones, floods, droughts and wildfires, graded Red (major), Orange (severe) or Green (moderate). UN OCHA and European Commission JRC.
Weather and climate disasters (10+ deaths, 100+ people affected, or a declared emergency or call for international help). CRED / UCLouvain, via Our World in Data.
FAQs
FAQs
How is the climate in Iran changing?
Iran is warming in line with the rest of the world. The page above shows the latest monthly temperature anomaly versus the 1961-1990 baseline, the long-term annual trend, and the region's rank in the historical record. The headline panel also shows the long-term trend rate per decade and the warmest and coolest years on file.
What is the climate like in Iran?
Iran has a arid climate (Köppen BSh: Hot steppe), with both a warm/cold cycle and a wet/dry cycle through the year. July is typically the warmest month, averaging 31.2°C, while January is the coldest at 6.5°C. Annual precipitation averages around 223mm (about 9mm of it as snow), concentrated mostly in the wet season.
Which climate drivers affect the weather in Iran?
Measured from seasonal temperature and rainfall in Iran since 1950, with the long-term warming trend removed (and ENSO's own share removed before scoring the other drivers), the climate drivers with a clear effect here are: El Niño / La Niña (ENSO) - strong, strongest in Aug-Oct rainfall, which El Niño tends to make wetter here (La Niña the reverse), about 31% of year-to-year variation; the North Atlantic Oscillation (NAO) - moderate, strongest in Jan-Mar temperature, which a positive NAO tends to make cooler here (a negative NAO the reverse), about 27% of year-to-year variation; the Arctic Oscillation (AO) - moderate, strongest in Jan-Mar temperature, which a positive AO tends to make cooler here (a negative AO the reverse), about 25% of year-to-year variation. Their current state is shown in the Climate Drivers section of this page.
What extreme weather affects Iran?
In 2024, the latest complete year, the international disaster database EM-DAT recorded 4 weather and climate disasters in Iran, against an average of 3.4 a year in 2015-2024, with 44 deaths. Over those ten years the most frequent type was flood (25 of 34) and the deadliest flood. GDACS, the UN and European Commission's disaster alert system, issued 0 Major (Red) and 0 Severe (Orange) alerts for Iran in the last 12 months. Live alerts are on this page and on the Extreme Weather tracker.
Where does the climate data for Iran come from?
Climate data for Iran comes from Our World in Data, sourcing Copernicus ERA5 and HadCRUT5 (national temperature anomaly) and the Global Carbon Project via Our World in Data (CO₂ emissions), refreshed every month, when the upstream temperature and rainfall data are refreshed.
What is the climate baseline used on this page?
Anomalies on this page are calculated against the 1961-1990 climatological baseline, which is the standard reference period used by the Met Office, NOAA, IPCC and most national climate services. Some panels also show the source-native 1901-2000 (NOAA) or 1991-2020 (WMO) baselines for verification. See Methodology & Sources for the full reference.
Which areas does the Iran climate data cover?
The Iran climate profile covers Tehran, Mashhad, Isfahan, Karaj and surrounding areas. Temperature, rainfall and emissions data for Iran
How often is the Iran climate update refreshed?
The Iran climate update is refreshed monthly, typically a few days after the previous month closes and the upstream provider (Met Office HadUK-Grid, NOAA Climate at a Glance, Copernicus ERA5 or the Global Carbon Project) publishes its update. See the Climate Rankings for cross-region comparisons.
What counts as a Heatwave Day on the Iran climate page?
Heatwave Days use the Warm Spell Duration Index (WSDI) - the WMO/ETCCDI-standard heatwave measure: days that are part of a run of 6 or more consecutive days above the local 90th-percentile temperature for that calendar day. The 90th-percentile threshold varies by time of year (a hot day in January is judged differently to one in July) but is fixed to the 1961-1990 baseline for every year shown - it does not shift as the climate warms, which is why Heatwave Days trend upward over time.
Does the Iran climate page include frost and snow data?
Yes. Frost Days (days with a minimum temperature below 0°C, World Bank CCKP) and snow water-equivalent (GPCC) are shown alongside temperature and precipitation, each measured against the 1961-1990 baseline where a like-for-like historical comparison is available.
What major climate events has Iran experienced?
Major climate events in Iran include The cold winter of 1972; The shrinking of Lake Urmia (1995-2025); The record heat of 2010 across the Middle East and North Africa. The Climate History panel on this page lists 36 sourced events and pattern shifts relevant to Iran, the earliest from 1912 - 3 about Iran itself and the rest global context such as volcanic eruptions and El Niño events. Each entry carries its own sources and can be searched, filtered to local events or by category, and sorted by date; scrolling the list moves a cursor across the chart above so you can see where each event falls in the record.
Where does the Climate History list for Iran come from, and how is it checked?
It is a hand-reviewed register, not an automatic feed. Every entry is sourced, and each one records how it was verified - against this site's own data series, against a peer-reviewed paper, or against the public record of the event. 19 of the 36 entries here are written specifically about Iran, usually quoting its own ranking or measured figures. The rest give global or national context shared with wider pages. Where a figure is narrower than it first appears, or a famous claim does not hold locally, the entry says so.