You are correct sir, I remember from my military training that it’s the relative humidity vs the temp that will mess you up!It's all relative, and air moisture can make a big difference too.
People rarely die from exposure to cold air, but submerge yourself in chilled water and it can be lethal within 15 minutes.
Then of course there's mental conditioning. In September I always shiver at temperatures just above freezing, but by March of the next year a clear and calm afternoon at just below freezing is suntanning weather.
Of course the air probably is more moist in September, Winter air on the Prairies is extremely dry and Autumn is maybe not quite dry enough yet, but I assume conditioning still has more of a role to play in the perception of cold from Fall to Spring.