Tehran, the capital of Iran, sits at the foot of the Alborz Mountains on the northern edge of the central Iranian plateau, with elevations rising from around 1,100 metres in the south of the city to over 1,700 metres in the north, at approximately 35.69°N, 51.39°E. Its altitude and inland position give it a cold semi-arid climate (Köppen BSk) with hot, dry summers and cold winters, and a marked temperature difference between the higher, cooler north and the lower, warmer south of the city.

Summer, from June to September, is hot, dry and sunny, with July the hottest month — average highs around 36–37°C — but the elevation and very low humidity make the heat far more bearable than in the humid lowlands, and nights cool off noticeably. Rain is essentially absent for months, and clear skies dominate, though the enclosed basin can trap air pollution over the city, especially when winds are light.

Winter, from December to February, is cold, with January the coldest month — average highs around 8°C and lows near or below freezing. Cold air spilling off the Alborz and occasional outbreaks from the north bring frost and several snowfalls each winter, which can settle for days, particularly in the higher northern districts. This is the main, if still modest, rainy and snowy season.

Tehran is dry, receiving only around 230 mm of precipitation a year, concentrated in the cooler months from late autumn to spring — winter and early spring are the wettest — while summer is almost completely rainless. A share of the cold-season total falls as snow, especially in the elevated north of the city. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Tehran's most distinctive climatic feature is the strong gradient across the city created by the Alborz Mountains: the affluent northern districts, hundreds of metres higher, are consistently cooler, wetter and snowier than the hotter, drier south. The mountains also feed the rivers and the ski resorts within easy reach of the capital, while the basin's tendency to trap cold air and pollution in winter is a persistent problem for the sprawling metropolis.

To follow any single measurement in Tehran more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.