Upper Torso - Light weight Long sleeved synthetic shirt. Sleeves up if its not sunny, down if it comes out.
Lower Torso -Synthetic running shorts
Feet -La Sportiva wildcats with darn tough coolmax socks
Head -Baseball hat if there is little sun forecast, wide brimmed if I expect to get more sun during the trip
Hands - nothing but poles
Extra Credit: What clothing changes if wind picks up? Probably no change at 40 degrees, but if it is an especially cold humid fall type breeze a windshirt or raincoat (depending on which I have along based on the expected conditions of the entire trip)