Can I plant out creeping Phlox now ie August.
I would wait until the heat waves of summer are past. It needs full sun to bloom heavily which will be hard for a new transplant to take when temps are high. Make sure you gradually get it used to full sun. If you decide to put it out now, construct some shade for 3-5 days, longer if it struggles in full sun. Water when the soil is dry 1" deep. Make sure it doesn't dry out if fall is dry. It needs to be well-hydrated going into winter.