Weather is probably a major factor when you plan your trip to Chillan, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually January and February, with an average temperature of 20°C, while the coldest months are July and August, with an average of 9°C. The rainiest months in Chillan are June, August, July and May, with each month seeing an average of 234 mm of rainfall.