Argentina's seasons are the reverse of the Northern Hemisphere. Summer runs December to February, winter June to August. The country spans nearly 4,000km from the subtropical north to the subpolar south, so the right time to visit depends heavily on where you are going.
Buenos Aires
Spring (October–November) and autumn (March–April) are ideal — mild temperatures, low humidity, and the city at its most pleasant. Summer (December–February) is hot and humid, and many porteños leave the city in January. Winter is mild and rarely very cold; it's a perfectly fine time to visit.
Patagonia
Go in summer (December–February) for trekking, glacier visits, and wildlife watching. Days are long, weather is warmest (though wind is always a factor in the south), and most services are open. Shoulder season — October to November, and March to April — is less crowded and can be beautiful. In winter, many lodges and parks close.
Northwest (Salta, Jujuy, the Andes)
April and May offer dry, clear days and striking light on the altiplano landscapes. Avoid the summer wet season (November–March) when roads can flood. The northwest is accessible year-round but is at its best in the dry season.
Iguazú Falls
The falls are most dramatic after rain, which means the wet season (November–March) produces impressive flows — but also intense heat and humidity. April to September is drier, cooler, and more comfortable for walking the trails.
Mendoza (wine country)
March is harvest season (vendimia), the best time to visit wineries and attend the Fiesta Nacional de la Vendimia. Autumn is also beautiful. Summer can be very hot in the vineyards.
Skiing
The ski season runs June to September. Bariloche and Las Leñas are the main resorts and get busy with Argentine and Brazilian tourists in July (school holidays).