Normal afternoon temps are in the 50' s to 70' s.
Normal morning temps are in the 30' s to 40' s.

Definitely be prepared for temps down to 25 in the morning and up to 80 in the afternoon. Bring the sunscreen and mosquito repellent.
Think layers for clothes. Leave the heavy coats. Be prepared to do some hiking in steep country and shed layers (all in natural tones so you remain camo' d) as you warm up.
Fleece jackets are a good outer garment.

Bring a day pack with you with all your necessary items:
Knife and sharpener, light bone saw, game bags, plastic sacks, light rope,
Extra ammo (if rifle hunting), compass, map of area, camera, 2 lightweight flash lights with extra batteries and bulbs, headlamp. Lightweight spare food, 1 liter water, water filter, binos, small first aid kit, mosquito repellent(lightweight), sunscreen(small tube),
bugle, couple of different cow calls.

Resist the temptation to dress too warm when you leave camp in the morning.
After a few minutes of hiking you will warm right up and you don' t want to have to carry all that extra clothing around with you all day.

Septembers are usually nice, the last few years they have been particularly warm with a couple days here and there of cold weather with a few snowshowers, snow is usually not an issue at that time of year.