Key Summary- Iran’s climate spans from arid deserts and semi-arid steppes in the interior to lush humid subtropical forests along the Caspian shore.
- The Alborz and Zagros mountain ranges create a powerful rain shadow, trapping moisture in the north and west while leaving the central plateau parched.
- Seasonal extremes are stark, with freezing winters in the northwest and stubbornly high heat and humidity along the Persian Gulf in summer.
At WeatherBox, our Köppen climate classification maps reveal Iran’s extraordinary climatic range. The country’s position between roughly 25°N and 40°N, combined with a high interior plateau and encircling mountains, produces sharply defined zones. Much of central and eastern Iran falls under BWh (hot desert) and BWk (cold desert), where annual rainfall rarely tops 150 mm (6 in). The western Zagros highlands experience a Csa (hot-summer Mediterranean) regime, with cool, wet winters and dry, hot summers. Along the narrow Caspian coastal plain, the Cfa (humid subtropical) climate delivers year-round moisture and mild temperatures. In the mountainous northwest, Dsa and Dsb (humid continental) climates bring snowy winters and mild summers.
The interplay of geography and wind is most visible on the Caspian coast. Moisture-laden northerly winds rise over the Alborz, wringing out over 1,000 mm (39 in) of rain annually on the northern slopes, while the leeward side remains a rain shadow desert. Farther south, the shallow Persian Gulf acts as a heat reservoir, feeding sultry air into the adjacent lowlands and creating extreme summer heat indices. In the central deserts, such as Dasht-e Kavir and Dasht-e Lut, summer temperatures can exceed 50°C (122°F), while winter nights sometimes dip below freezing in the cold desert basins. In the southeast, an arm of the South Asian monsoon occasionally reaches the Makran coast, delivering erratic summer rainfall that supports a BSh (hot semi-arid) steppe. Winter transforms the northwestern highlands, where sub-zero temperatures and heavy snow are common, at the same time the southern plains enjoy mild daytime highs around 15–20°C (59–68°F).
