Chicago, also known as the Windy City is known for its cold weather. However, in the summer months of May, June and July, the region sees some warm and balmy days during which the day time temperature goes as high as 80 to 85 °F. Even the evening temperatures are comfortable at 61 to 66 °F. The citizens of and visitors to Chicago never miss these warm days and usually enjoy with their families and friends in the many outdoorsy fun activities Chicago has to offer.
Chicago climate overview
http://en.wikipedia.org/wiki/Chicago#Climate
One of the best places to visit during warm days in Chicago is the Grant Park. Located in downtown Chicago, the park offers large open and green spaces with the famous Millennium Park, Art Institute of Chicago and Buckingham Fountain. This park plays host to many events like the Chicago Jazz Festival and has lengths of shaded walkways which makes it a popular joggers, walkers and picnickers. There are several out door restaurants, softball fields, tennis courts, and yoga centers in the park.
Grant Park
http://www.aviewoncities.com/chicago/grantpark.htm
You can also visit the Lincoln Park Zoo which is one of the oldest public zoos in USA. A favorite attraction among the grown ups and children alike, the Lincoln Park Zoo is home to zebras, lions, African apes and many other exotic animals and birds from around the world. The children and young visitors especially enjoy the Treetop Canopy Adventure and Farm in Zoo, which are educational and entertainment setups within the zoo area.
Lincoln Park Zoo
http://www.aviewoncities.com/chicago/lincolnparkzoo.htm
Another great place to visit during summer days in Chicago is the Shedd Aquarium. Built in 1924, this is the first aquarium to house a permanent seawater fish exhibit. The prominent collections in display are Amazon Rising, a recreation of the jungles of Amazon, Caribbean Reef, and the Wild Reef. Some of the exotic creatures you can see in the Shedd Aquarium are Beluga Whales, Alaska Sea Otters, Pacific white sided dolphins, Green Sea Turtles, and Australian Lungfish.
Shedd Aquarium
http://en.wikipedia.org/wiki/Shedd_Aquarium