Since you're unlikely to flit from region to region, you could probably manage to visit every part of the country at the optimal time of year. Roughly falling in September to November, the Argentine spring is perfect just about everywhere except parts of the south, where icy gales may blow, while autumn (March and April) is great for the wine- harvest in the Cuyo and the red and orange hues of the beeches down south. Above all, you're best off not being in the far south in the coldest months (April-Oct), or in the Chaco and some lowland parts of the northwest in the height of summer (Dec-Feb). On the other hand, summer's the only time to climb the highest Andean peaks and the most reliable time of year to head for Tierra del Fuego. Buenos Aires can get unbearably hot and sticky in midsummer and may come across as somewhat bleak in midwinter (July and Aug) - though that's when you should aim to be in the skiing resorts. A final point to bear in mind: the national holidays are roughly January, Easter and July, when transport and accommodation can get booked up and many resorts are packed out.