Brazil is located in Southern hemisphere. So, it is winter in much of Brazil, although Rio de Janeiro is close enough to the equator, so it will not be cold for the Summer Games.
Also, Rio de Janeiro is quite close to the equator. Therefore, the temperatures do not swing as much as they do in other areas. For example, temperatures may swing by just 10 degrees Fahrenheit over the course of an entire year.
Rio Olympics are going quite good. However, global warming will make it nearly impossible to hold the summer olympics in future.
Here is a patent application on outer space sun screen for reducing global warming.
Publication number: US20080203328 A1
Patent Title: Outer space sun screen for reducing global warming
Publication date: 28 Aug 2008
Filing date: 22 Feb 2008
Priority date: 22 Feb 2007
Inventors: Yoram Palti
Original Assignee: Yoram Palti