Yes u can plan Delhi in August There are number of places to be covered in Delhi
Red fort Qutub Minar Hamayun tomb Gurudwara Bangla Sahib
Gurudwara Sis Ganj Sahib India Gate
I personally feel Delhi is always awsome except the month of May - June due to heat waves and the kind of hot weather here is dificult to handle..rest visiting in monsoon is not the problem... do enjoy the famous food joints...