Depends very much on what altitude you are going to reach. Even in July and August, some high climbs, depending on how low a elevation you start will have you going through two if not three different climates resulting in very cold at the top where you'll get hypothermia if you linger up there long after reaching the top without sufficient clothing. July and August are also the dates that most will be decent weather for a inexperienced climber.

Search the internet for local cycling clubs that have published some information on those places you are interested in. Sometimes the local government's will have some info about the popular ones that help bring it tourism dollars.

Also, this website has a lot of good infomation about climbs all over the world. Sometimes it's a little hard to use it's search tool as the climbs may be under different names than you expect. Moving the map to where you want to search will bring up a lot of results if you zoom in.

PJAMM Cycling

I also got some help by asking here in the Regional Discussions section of BF about climbing what is now called Mt. Blue Sky in CO.