This page presents Iran, Islamic Rep.'s climate context for the current climatology, 1991-2020, derived from observed, historical data. Information should be used to build a strong understanding of current climate conditions in order to appreciate future climate scenarios and projected change. You can visualize data for the current climatology through spatial variation, the seasonal cycle, or as a time series. Analysis is available for both annual and seasonal data. Data presentation defaults to national-scale aggregation, however sub-national data aggregations can be accessed by clicking within a country, on a sub-national unit. Other historical climatologies can be selected from the Time Period dropdown list. Data for specific coordinates can be downloaded for in the Data Download page.
The country’s climate is mainly arid and semiarid, except the northern coastal areas and parts of western Iran. The climate is extremely continental with hot and dry summer and very cold winter particularly in inland areas. Apart from the coastal areas, the temperature in Iran is characterized by relatively large annual range, about 22°C to 26°C. The rainy period in most of the country is from November to May followed by dry period between May and October with rare precipitation.
The average annual rainfall of the country is about 240 mm with maximum amounts in the Caspian Sea plains, Alborz and Zagros slopes with more than 1,800 and 480 mm, respectively. Iran has climatological diversity with three types of climate: 1) dry and semi-dry climate: large parts of internal lands and southern border of Iran have this climate; 2) Mountainous climate, which itself is subdivided
into two categories of cold and moderate mountainous climate; 3) Caspian climate: narrow and small area between Caspian Se and Alborz Mountain Belt with 600-2000 mm annual rain.
- The trend of increase in maximum temperature of 0.03°C/decade, while minimum temperature trend increase of 0.06°C/decade were observed, which is double of the maximum temperature trend during the period (1975- 2010).
- Trends of maximum and minimum temperatures changes in winter are more than those of in summer. In other words, the trends of maximum and minimum temperatures in winter are 0.05 and 0.07°C/decade and those of summer are 0.02 and 0.06°C/decade, respectively. Minimum temperature trend being double of maximum temperature trend has been proven in other studies.
- The trend for maximum temperature is between 0.2-0.3°C/decade and that of minimum temperature is between 0.4-0.5°C/decade.
- The trend of annual rainfall changes is not significant and is less than -1 mm per decade (1975 – 2010).
- The greatest decline in rainfall is experienced in the west of Iran (-3.34 mm/decade) and center of Iran was the only region with increased precipitation (0.11 mm/decade) (1975 – 2010).