Climate
Rosario logs 6 frost days a year to San Juan's 18 — Rosario wins by 12. Rosario also leads on hot days by 67.
Rosario
Feels-like °C
Dinner outside
San Juan
Feels-like °C
Dinner outside
Air Quality
Rosario averages 12.6 µg/m³ (moderate) PM2.5 annually versus San Juan's 19.1 µg/m³ (sensitive-groups) — Rosario breathes ~34% cleaner air (6.5 µg/m³ lower).
Rosario
San Juan
PM2.5 annual average
WHO classification
City Scale
Both maps at the same real-world scale — 1 cm on either map is the same distance.
Rosario (1.2M) and San Juan (465K) are 2.6x in population — Rosario is the larger metro, San Juan the smaller; on land area Rosario spans roughly 1.8x more ground.
Rosario is roughly 2.2x the scale of San Juan
Combined population & area comparison
RosarioSan JuanCity Scale Rankings
Rosario1.2M2.6xSan Juan465K1xRosario199 km²1.8xSan Juan109 km²1xRosario
San Juan
Who Thrives Here
Rosario is the stronger fit for the clean air seeker. Both cities work well for the sunshine lover.
Also compared
Barcelona 
Berlin 
MiamiFrequently asked about Rosario vs San Juan
▶How does the climate compare between Rosario and San Juan?
▶Should I move to Rosario or San Juan?
The best city depends on what matters to you
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