In reply to Joedt:
There are a lot of places you can get to from Chicago with a 2 week window (if driving--more,of course, if you fly). It will still be hot most places so you want altitude. Are you interested in mountain routes or just crags/bouldering? Colorado is your best bet--about a solid days drive to the southwest will get you to the Denver/Boulder area. The lower areas around Boulder will be hot, but definitely climbable in the shade--and you can always find shady climbs there. An hour west (and 'up') you've got the areas around Estes Park--mountaineering--primarily on rock--in Rocky Mountain National Park, but also high altitude cragging and bouldering---Lumpy Ridge--great area right outside of town, the Monastery, etc. Just watch out for afternoon thunderstorms. Plenty of other areas not much further away in Colo--such as Mt. Evans--cragging and bouldering, South Platte, Pikes Peak area---tons of options and all worthwhile. Most areas I've mentioned are primarily trad but some sport areas as well.
About the same distance from Chi. but more directly west is the Black Hills area of South Dakota and Wyoming. The Custer/Sylvan Lake Needles--mostly trad and the Rushmore Needles--sport--are large collections of pinnacles of crystalline granite--lots of routes--up to 3 pitches (mostly single pitch). Nearby are also limestone sport areas--Spearfish Canyon is the best known. These are all in the South Dakota area of heavily forested hills--not very high altitude but usually nice temperatures at that time of year. A bit west over the line in Wyoming is Devil's Tower--an amazing, must-climb formation--it is circular so something is always in the shade. Further west in Wyoming are several lifetimes worth of climbing.
Those are the best bets if driving (there are good cragging areas closer to Chicago in southern Illinois (Jackson Falls), Wisconsin (Devil's Lake), Kentucky (Red River Gorge) but all will likely be hot and humid in late August). If you want to fly places, then areas such as the California Sierra have plenty of options--Tuolumne in Yosemite National Park, Shuteye Ridge,the areas around Lake Tahoe (Donner Summit, Lover's Leap), plenty of other options.
Post edited at 21:45