Tucson sits in a valley of the Sonoran Desert in southern Arizona, ringed by mountain ranges at around 730 metres above sea level and approximately 32.22°N, 110.93°W. It has a hot desert climate (Köppen BWh) — with scorching summers and mild winters — and a distinctive summer rainfall maximum from the North American monsoon.

Summer, from May to September, is scorching, with June the hottest month — average highs around 39–40°C, frequently exceeding 43°C — under a relentless sun, though the desert dryness makes the heat more bearable than humid climates. From early July the North American monsoon arrives, bringing dramatic afternoon thunderstorms, spectacular lightning and brief flash floods through September.

Winter, from December to February, is mild and sunny, with January the coolest month — average highs around 19–20°C and cool nights near 4–5°C, occasionally dropping to frost. Pacific storm systems bring modest winter rain, and snow occasionally dusts the surrounding peaks. This mild, bright stretch is comfortably the best time of year in the desert.

Tucson is very dry, receiving only around 300 mm of rain a year, with a pronounced July-to-September maximum from the monsoon and a secondary winter peak from Pacific storms, while May and June are almost entirely rainless. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Tucson's year is punctuated by the North American monsoon, when a shift in the winds draws tropical moisture north from the Gulf of California, transforming the parched desert with violent afternoon thunderstorms, dust-laden haboobs and flash floods racing down normally dry washes — the defining weather event of the Sonoran summer.

To follow any single measurement in Tucson 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.