First and foremost, I would bring an extra shirt layer over what you felt comfortable with in the morning. If there’s a chance of rain, this could be a rain jacket.
With your core warm and dry, think about packing a small super-absorbent trail towel. You could buy an expensive beauty that will hold ungodly amounts of water, but I usually pick up a cheap shammy cloth, so I don’t feel bad using it for something other than drying off such extra strap padding, gauze pad for a duct tape bandage, cooling pad, handkerchief, or even toilet paper. Plus, since it’s replaceable, you don’t mind washing it (often!) or cutting it to size for a specific application.
Those two items, along with a hat, get you a long way, but there are a couple more clothing items I take on occasion. If I am going on a longer hike or on a wet or dusty trail, I think about taking an extra pair of socks. With a pair and a spare, you can wear one and wash one to get you through most any situation. Also, I love gloves for cold weather hiking. The colder the weather, the thicker the gloves.
Pro-Tip: Buy the same brand (i.e. matched) socks and liners so the wick at the same rate