Weather is probably a major factor when you plan your trip to Buenos Aires, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and September with an average temp of 69°F, while the coldest months are January and July with an average of 68°F. The rainiest months in Buenos Aires are April, November, October, and December, with each month seeing an average of 12 inches of rainfall.