December marks the official arrival of summer across Argentina, bringing a sharp contrast between the sun-baked northern tropics, the warm and humid pampas, and the crisp, windswept wilderness of the deep south. Because the country stretches nearly 3,700 miles from north to south, a single weather rulebook doesn't work. You might sweat through a humid afternoon in Iguazú at 32°C (90°F) while wearing a fleece jacket against the wind in Ushuaia where temperatures hover around 13°C (55°F).
Understanding regional climate variations is essential before locking in your itinerary or packing your bags. This guide breaks down what to expect across Argentina's distinct microclimates during December, how to handle sudden summer storms, and exactly what gear to pack for a multi-region trip.
Regional Weather Breakdown for December
Argentina's vast geography creates vastly different atmospheric conditions depending on where you stand. Here is how the weather behaves across major regions during the first month of summer.
Buenos Aires and the Central Pampas
Buenos Aires shifts into high gear in December. Daytime highs average 29°C (84°F), but high humidity often makes it feel significantly hotter. Mornings are generally bright and ideal for walking the neighborhoods of Palermo or San Telmo, but afternoon heat can build quickly.
December is also known for sharp, dramatic summer thunderstorms in the capital. These storms drop heavy rain over a short period, often clearing the air and bringing a brief respite from the muggy heat.
Patagonia and the Lake District
While the north bakes, Patagonia enjoys its warmest and most accessible month of the year. In San Carlos de Bariloche and the Lake District, daytime temperatures average a comfortable 21°C (70°F), with crisp nights dropping to 6°C (43°F).
Further south in El Calafate and Ushuaia, summer means long daylight hours—often up to 17 hours of sunlight—giving you plenty of time to explore glaciers and coastal fjords. However, Patagonia's notorious wind is a constant factor. Clear blue skies can turn into gale-force gusts within an hour, making windproof outer layers mandatory regardless of sunshine.
Iguazú Falls and the Northeast
The northern subtropical provinces, home to Iguazú Falls, experience intense heat and heavy humidity. Average highs reach 31°C (88°F) to 32°C (90°F). December is part of the regional wet season, meaning sudden, torrential downpours are common.
The silver lining? High water levels make the massive cascade systems thunder with maximum force. Be prepared for mist, humidity, and sudden tropical cloudbursts that soak everything in minutes.
Mendoza and the Cuyo Wine Region
Mendoza is dry, sunny, and hot in December. Daytime temperatures regularly push past 30°C to 32°C (86°F to 90°F). Rainfall is minimal, averaging only a few wet days for the entire month.
The dry heat makes vineyard tours and outdoor tastings comfortable in the mornings, but shade and hydration become critical by early afternoon.
Understanding Summer Storms and Climate Quirks
Travelers often assume December across South America means uninterrupted sunshine. In reality, Argentina's summer weather brings specific atmospheric patterns you need to factor into your daily planning.
The Dynamics of Humidity and Heatwaves
In Buenos Aires and the central agricultural belt, stationary high-pressure systems can trigger multi-day heatwaves where temperatures stay elevated even after sundown. Concrete retains heat heavily in the city centers. Air conditioning is standard in hotels and restaurants, but older apartment rentals may struggle to keep up during peak afternoon spikes.
Mountain Weather Volatility
In the Andes and Patagonia, local topography dictates the weather. A sunny morning in Bariloche or Torres del Paine can deteriorate rapidly as moist air rolls in from the Pacific, hitting the mountain range and dropping sudden rain. Local guides often check barometric pressure trends rather than standard weather apps, which struggle to predict micro-shifts in mountainous terrain.
Smart Packing Strategies for Argentina in December
Because you will likely cross multiple climate zones if you visit both Buenos Aires and Patagonia, packing light requires careful layering. Avoid heavy denim or thick cottons that trap moisture and take days to dry.
Clothing for Warm Regions (Buenos Aires, Iguazú, Mendoza)
- Breathable linen or lightweight merino wool shirts
- Quick-drying shorts and skirts
- A light rain jacket or compact travel umbrella for sudden urban storms
- Comfortable walking shoes with good ventilation
- Smart-casual evening wear for dinners in urban centers
Gear for Cool and Windy Regions (Patagonia, Ushuaia)
- Moisture-wicking base layers (thermal tops and bottoms)
- Insulating mid-layers like fleece or lightweight grid-fleece jackets
- A windproof and waterproof shell jacket
- Sturdy, broken-in hiking boots with ankle support and reliable grip
- Accessories including a wool beanie, lightweight gloves, and a buff or neck gaiter for high winds
Essential Travel Accessories
- High-SPF sunscreen and UV-blocking sunglasses (the Patagonian ozone layer thinning makes solar radiation intense)
- High-deet insect repellent for Iguazú and northern wetlands
- A universal power adapter (Argentina primarily uses Type I plugs, though some hotels accommodate Type C rounds)
- A durable 20–30L daypack with a built-in rain cover for excursions
For more detailed regional gear lists, check the Argentina Pura Patagonia Packing Guide. To understand urban microclimates and local packing essentials, review the Mente Argentina Buenos Aires Guide.
Common Mistakes to Avoid in December
Planning a December trip without understanding local weather realities leads to unnecessary discomfort. Here are four common pitfalls to sidestep:
- Underestimating Patagonian wind: Packing only light windbreakers without a heavy-duty shell will leave you freezing during glacier boat tours or valley hikes.
- Skipping rain protection for Iguazú: Relying on cheap plastic ponchos bought on-site is risky; bring a reliable, breathable waterproof jacket that won't trap jungle humidity.
- Scheduling heavy outdoor activities at midday: In Mendoza, Salta, and Buenos Aires, walking outdoors between 1:00 PM and 4:00 PM during a heatwave drains your energy fast. Shift strenuous activities to the early morning.
- Assuming uniform weather: Packing exclusively summer beach clothes because "it's summer in Argentina" will leave you shivering during evening outings in southern Patagonia or the high Andean plateaus.
Frequently Asked Questions
Is December a peak tourist month in Argentina?
Yes. Domestic travelers and international visitors flood popular spots like Bariloche, El Calafate, and Iguazú starting mid-December through the New Year holiday. Booking transport, accommodation, and major excursions months in advance is essential.
Do I need to book Iguazú Falls visits across multiple days?
Because December brings sudden heavy downpours and high humidity, scheduling two days at Iguazú gives you a safety buffer. If a torrential storm closes a trail or ruins a morning view, you have a second chance to explore the park.
How do I handle currency and cash needs while traveling between regions?
While major cities accept credit cards widely, smaller towns in Patagonia and national park entry gates often experience connectivity issues or cash-only limits. Keep a mix of Argentine Pesos and US Dollars accessible, and notify your bank before departure.
Are mosquitoes a major issue at Iguazú Falls in December?
Yes. Warm temperatures and heavy rainfall create prime breeding conditions for mosquitoes in the subtropical north. Pack a high-strength insect repellent containing DEET or picaridin, and consider wearing lightweight, long-sleeve clothing during forest walks.
