Lima Air Quality
South America's most polluted major capital. The Humboldt Current creates a coastal inversion that seals 11 million people under a grey ceiling of trapped vehicle exhaust for 6–8 months each year.
Monthly AQI
July is typically the worst month — marine inversion is strongest mid-winter
The Marine Inversion Explained
How It Works
The Humboldt (Peru) Current brings cold water northward along South America's Pacific coast. This cold ocean surface chills the marine air layer, making it denser than the warm air above — creating a temperature inversion.
The inversion lid sits at 800–1,200m during austral winter. Lima sits at just 154m above sea level, well below the inversion ceiling. All pollution emitted at street level circulates within this sealed atmospheric box.
Why It Persists
The Humboldt Current is semi-permanent — it flows year-round, but the inversion it creates is strongest May–November (austral fall through spring). During this period, Lima receives almost zero rainfall to flush pollutants.
The only natural ventilation is from sea breezes during afternoon hours, which push some pollution inland. By evening, the air stagnates again and PM2.5 concentrations rebuild overnight.
Health Advisory
Healthy Adults
Limit outdoor exercise during July–October peak season. Morning rush hours (7–9am) have the highest PM2.5 concentrations. Afternoon sea breezes typically improve air quality by 3–6pm.
Sensitive Groups
Children, elderly, asthma patients, and those with cardiovascular conditions should wear N95/KN95 masks during May–October. Keep windows closed during morning hours. Use air purifiers indoors if available.
Outdoor Workers
Construction workers, street vendors, and other outdoor workers face elevated PM2.5 exposure year-round. MINSA recommends protective masks for workers with ≥8 hour outdoor exposure on days when AQI exceeds 100.
Travelers to Lima
January–March is the best time to visit for air quality. If visiting in July–October, stay in Miraflores or Barranco coastal districts where sea breezes provide better ventilation than central/eastern districts.
Frequently Asked Questions
What is Lima's air quality index in 2024?
Lima's annual average AQI in 2024 was approximately 82 (Moderate to Unhealthy for Sensitive Groups). PM2.5 averaged 17.6 μg/m³ — 3.5× the WHO annual guideline. Lima has some of the worst air quality among Latin American capitals.
Why does Lima have such bad air quality despite being a coastal city?
Lima sits under a semi-permanent marine temperature inversion caused by the cold Humboldt Current. This inversion acts as a lid, trapping all vehicle exhaust and industrial emissions below 800–1,200m for most of the year (especially May–November). The grey overcast sky (garúa) is a visual sign of the inversion layer.
When is Lima's air quality best?
January–March (austral summer) is Lima's cleanest period. The inversion weakens, sea breezes are stronger, and occasional rains help remove particles. PM2.5 drops to 10–12 μg/m³ during these months.
Is the air safe to breathe in Lima?
For healthy adults on average days, Lima's air is breathable but exceeds WHO guidelines year-round. During the austral winter (July–October), sensitive groups — children, elderly, and people with asthma or heart conditions — should limit prolonged outdoor exercise and wear N95/KN95 masks during peak traffic hours.
How does Lima's air quality compare to other South American capitals?
Lima typically ranks as the most polluted major South American capital by annual PM2.5. It exceeds Bogotá (15.8 μg/m³), São Paulo (14.2 μg/m³), and Santiago (16.4 μg/m³) in most IQAir rankings. Only some smaller cities and industrial zones in the region exceed Lima's annual average.