Chile is nearly 3000 miles long north to south about the equivalent on Edinburgh to Baghdad so you will get a huge variation in climate. If that answers your question ...ok. but if not you are going to have to be more specific I'm afraid....Nei.
Travelled on Celebrity Infinity Valparaiso to Buenos Aires December 2006. Weather was very hot for pre-cruise days in Santiago and post-cruise Buenos Aires. Short sleeve summer clothes. Some ports were like UK spring weather - jumpers and light fleece. Ushuaia was cool. We may have been lucky but had no rain or really bad weather. The answer is take layers and in the most southerly ports carry warm and waterproof extras even if day starts off bright. The majority of passengers dressed elegantly for formal evenings, mostly dinner suit or dark business suit, and evening/cocktail dresses. Those not wishing to dress up used the self service buffet. Other evenings people were smartly dressed in a more informal way. This is a large ship with passengers from all over the world with different dress codes so you really can't take the wrong things.