Santiago sits in a broad valley in central Chile at around 500–650 metres elevation, hemmed between the Chilean Coast Range and the towering Andes, roughly 85 km from the Pacific at approximately 33.45°S, 70.67°W. It has a Mediterranean climate (Köppen Csb) with hot, very dry summers and mild, relatively wet winters — though total rainfall is so low that the climate borders on semi-arid. Being in the Southern Hemisphere, its seasons are the reverse of the Northern.

Summer, from December to February, is warm to hot, sunny and extremely dry, with January and February the warmest months — average highs around 27–30°C, and heatwaves that have topped 39°C. The city's altitude means summer nights cool off pleasantly, sometimes even feeling chilly after a scorching afternoon, and the dry air makes the heat more bearable than the same temperature on a humid coast. Rain in these months is essentially unheard of.

Winter, from June to August, is mild by day but cold at night, with July the coolest month — average highs around 14–15°C and lows near 3°C, occasionally dropping below freezing. This short season brings almost all of the year's modest rainfall. Snow in the city itself is very rare, falling only every few years, though the Andes just east are reliably snow-covered, feeding ski resorts within an hour's drive.

Santiago is strikingly dry, receiving only around 250–350 mm of rain in an average year — among the lowest of any capital — and it is heavily concentrated in the winter months from May to August, with June typically the wettest. The summer half of the year is effectively rainless, and recent years of drought have pushed totals even lower. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Santiago's valley setting, ringed by mountains, is also its biggest weather drawback: in winter, temperature inversions trap cold air and pollution in the basin, producing thick smog that regularly ranks the city among the more polluted in the Americas. The same enclosed geography, combined with the rain-blocking Coast Range and the altitude, is what keeps the air so dry and the skies so consistently clear the rest of the year.

To follow any single measurement in Santiago 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.