Chile is a long and narrow country and for this very reason if you go to the north you will find warmer climates and if you go to the south a much colder and rainy climate.
Santiago de Chile, which is where you are likely to arrive, if you look at the map, is right in the middle and the 4 seasons of the year are quite marked.
When to travel to Chile:
I recommend to travel to Chile in spring, between September and November, at this time the weather becomes very pleasant, already warmer to walk with a light sweater in the afternoon. Unlike traveling in summer (between the third half of December and February), in spring the prices will be lower and everything will be less crowded, because it is out of the high season.