Weather in Rosario in December

Shoulder season. December sits in between. You will get good days and you will lose some. Highs average 31.5 °C, lows 17 °C, and rain falls on 11 days — nothing in the month is working against you.

December ranks 11 of 12 — near the bottom of Rosario's year. August is the month that works, and the swing between the two is 37 points, which is a different holiday rather than a slightly better one.

Rain on 11 days, 4 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 31.5 °C days and 17 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 6 days clear 35 °C, so a serious heatwave is normal rather than notable. Across the twenty years measured, the hottest December day reached 41.9 °C and the coldest night fell to 9.3 °C, and the wettest single day dropped 242 mm — roughly 170% of the month's rain in one day.

December is moderately variable: 33 mm in the driest year against 434 mm in the wettest, around an average of 142 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind is light at 7.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 60%.

How December sits in the year

Temperatures hold steady either side: 29.1 °C in November, 31.5 here, 32.9 in January. Nothing about the timing within the month matters much.

Daylight in December

December is at or near the longest days of Rosario's year: 14.3 hours of daylight, holding steady all month. Evenings are the real gain — dinner outdoors still happens in full light.

An inland climate

With no coast nearby, the year swings a fair way — 27.9 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage. Within December itself the daily swing is 14.5 °C, so mornings and afternoons need different clothes.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

December in Rosario versus nearby

If Rosario is one option among several, the nearby comparison is worth making. Buenos Aires is a better bet in December — 5.5 °C cooler, 3 days less rain. Córdoba is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: December is a compromise. August is 32 points better and is what Rosario is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Rosario

See all twelve months in Rosario, or where else to go in December.