Chance of warm weather is far higher than cold weather. Last fall, the September season did get a few days with frost at night, which improves the hunting as bullwinkle doesn't move much in warm weather.
Rain gear should be good stuff as it can rain hard and rain sideways. Its more important that your rain gear be quiet and actually waterproof than anything else. Camo is NOT necessary.
I got my bull on one of these rainy days during the second week of the season. My rain parka had Florida Keys blue, the guide was wearing dark blue work gear. We walked/stalked from about 250 yard up to about 65 yards, all in front of the bull, before shooting. The wind was in our favor, blowing hard, making it rain sideways, as I mentioned.
Be aware that there is no hunting on Sunday until October.
Good hunting!