Santiago, Chile, has a Mediterranean climate with warm, dry summers and cool, wet winters. Average temperatures range from highs of 30°C (86°F) in January to lows of 4°C (39°F) in June and July, making it one of the most temperate major cities in South America. Its location in a valley between two mountain ranges shapes nearly every aspect of its weather, from rainfall patterns to air quality.
Mediterranean Climate With Dry Summers
Santiago falls under the Csb classification in the Köppen climate system, meaning it has a warm-summer Mediterranean climate. In practical terms, this means the city gets almost all of its rain during the cooler months (May through August) and stays dry through the long summer stretching from November to March. If you’ve spent time in places like coastal California or parts of southern Europe, Santiago’s seasonal rhythm will feel familiar.
The northwestern outskirts of the Santiago metropolitan area, near Batuco and Lampa, actually qualify as semi-arid, receiving even less rain than the city center. This gradient hints at how quickly conditions shift across the basin depending on elevation and proximity to the mountains.
Monthly Temperatures
Summers in Santiago are genuinely hot. January, the warmest month, averages a high of 30°C (86°F) with overnight lows around 13°C (55°F). February is nearly identical. The large swing between daytime and nighttime temperatures is a signature of the city’s inland, valley position. Even on the hottest days, evenings cool off noticeably.
Winter is mild compared to cities at similar latitudes in the Northern Hemisphere. June and July average highs of just 15°C (59°F), with lows dropping to about 4°C (39°F). Frost can occur on the coldest nights but snow in the city itself is rare. The transition seasons, March through May and September through November, are comfortable, with highs in the low to mid-20s°C (70s°F) and gradually shifting rain patterns.
| Season | Typical Highs | Typical Lows |
| Summer (Dec–Feb) | 28–30°C / 82–86°F | 10–13°C / 50–55°F |
| Autumn (Mar–May) | 19–27°C / 66–81°F | 6–11°C / 43–52°F |
| Winter (Jun–Aug) | 15–17°C / 59–63°F | 4°C / 39°F |
| Spring (Sep–Nov) | 19–25°C / 66–77°F | 5–8°C / 41–46°F |
Rainfall and the Ongoing Drought
Santiago typically receives most of its annual precipitation between May and August, with the rest of the year staying largely dry. But “typical” has shifted. Central Chile has been experiencing what scientists call a megadrought, with roughly 30 percent less rainfall than normal over the past decade-plus. In 2019, the deficit reached 80 to 90 percent in some areas, leaving the semi-arid zones north of Santiago almost completely without water and turning green landscapes visibly brown.
This prolonged dry spell is not a temporary fluctuation. It represents the kind of sustained rainfall decline that changes water availability, agriculture, and daily life across the region.
Why the Valley Matters
Santiago sits in a basin flanked by the Andes to the east and a lower coastal range to the west. The Andes intercept moisture carried by winds from the east, creating a rain shadow effect that keeps the city drier than the land on the other side of the mountains. This same geography traps air inside the valley, which has major consequences for both temperature and air quality.
During afternoons, the uneven heating of the valley floor and surrounding slopes generates a steady wind blowing west to east. At night, the wind drops to near zero across most of the valley, with only a faint breeze near the mountains caused by cooling slopes. This daily cycle means Santiago’s air can stagnate, especially in the cooler months.
Winter Air Quality
The combination of a valley setting, calm winds, and cold air creates a problem Santiago is well known for: winter smog. Temperature inversions, where a layer of warm air sits on top of cooler air near the ground, occur only in winter and can extend up to about 400 meters above the surface. These inversions act like a lid, trapping fine particulate pollution (PM2.5) close to street level.
On days with a full inversion, particulate concentrations are noticeably higher and wind speeds are at their lowest. The worst pollution peaks happen at night and in the early morning hours, when air movement is minimal and emissions from heating and traffic accumulate in the stagnant air. Santiago has implemented driving restrictions and industrial controls during these episodes, but the geography makes the city inherently vulnerable to poor winter air quality.
Summer Humidity and UV Exposure
Despite the heat, Santiago’s summers are relatively comfortable because the air stays dry. January humidity averages around 54 percent, the lowest of the year, so the 30°C highs feel less oppressive than they would in a tropical city. By contrast, winter humidity climbs to about 83 percent in June, which can make the cool temperatures feel damper and chillier than the numbers suggest. The yearly average sits around 70 percent.
What does demand attention in summer is ultraviolet radiation. Santiago’s UV index routinely reaches 10 in December and January, a level classified as “very high” by global health standards. On clear days, the index can push even higher. Chile’s proximity to the Antarctic ozone hole contributes to elevated UV levels across the country, and Santiago’s altitude (roughly 500 meters above sea level) reduces the atmosphere’s filtering capacity slightly. Sunburn can happen fast, even on days that don’t feel excessively hot.
Heatwaves and Extremes
Santiago occasionally experiences heatwaves that push temperatures well beyond the seasonal averages. On January 31, 2024, the city recorded 37.3°C (99°F), the third-highest temperature in 112 years of record-keeping. That event coincided with devastating wildfires in other parts of Chile, fueled by the same extreme heat and dry conditions.
These heat extremes are becoming more notable against the backdrop of the megadrought. With less soil moisture and sparser vegetation, the landscape absorbs and radiates more heat, amplifying already warm conditions. While Santiago has always had hot spells in January and February, the combination of drought and rising peak temperatures is pushing the upper boundary of what residents and infrastructure are built to handle.