Below are my notes for visiting Argentina. These travel tips for visiting Argentina are obtained from a variety of sources including some of the following: my first hand observations, personal conversations, magazines, newspapers, websites, books and so forth.
Best Time to Visit Argentina
Short Answer: All year Argentina has somewhere good to visit. March and April are best in my opinion, followed by October and November. Unless skiing or interested in the north, I believe the least attractive time is June through August.
December through February: Southern Argentina (Patagonia, Tierra del Fuego) is a good choices at this time of year. I visited Iguazu Falls in January when waterflow (and visitors and rates) is at its peak and the landscape green (but at its hottest and rainiest). As a reference, January is the warmest month of the year in Argentina so Iguazu and Buenos Aires can be quite warm and humid. Generally, crowds higher in the austral summer especially at beaches and getaway towns, and rates are higher. Buenos Aires is not jammed but can be hot as mentioned.
March, April, May: Crowds Lessen & Weather Great. Wine Harvest in Mendoza area, Foliage Changing in Patagonia which still is passable, etc. Tierra del Fuego gets more dicey. (Easter can be busy, especially Iguazu Falls)
June, July & August: Winter sports/skiing in the mountains. Much of the south is in hibernation. July can be busy. Can visit Iguazu (waterflow is lessening but dryer skies) and other points in the north (Salta, Atacama, etc).
September through November: Great time to visit Buenos Aires, especially October & November. Mid-October and November are great times to visit much of the country (Tierra del Fuego is better in the austral summer).
Miscellaneous Travel Tips for Argentina
The long-distance buses were very comfortable.
Research whether there is a travel visa or fee to visit. For a while, Argentina was charging visitors from certain countries more than $150USD to visit but recently that has disappeared (I believe temporarily so make sure you check).