I would like to know if I can cut down Perennial Geraniums now or if I do it now will I kill them?
The reason why I want to do this is to spray any weeds that are in with them, I do not want to kill them. If I would cut them down now will they come back yet?
It has been very dry here in Northwest Ohio, I have clay soil.
Any advice would be very welcome.

Well, I just cut down two monster 'Rozanne' geraniums, dug 'em up and relocated them --in the high heat of summer no less--so I sure hope they'll come back, next year at least!

Anyway, geraniums are very durable in general and many, like macrorrhizum, the big-root geranium, will come back from healthy rhizomes. Cutting them back won't kill them. Spraying them with weed killer will, though, so you'd have to be very careful with that.

Maybe you could just cover the geraniums with something -- like an upside-down bucket ? and then spray around them. (I would suggest using a weed killer that doesn't have 'soil activity' - like Roundup, for instance).