Agree its all down to psychology, september is not that much cooler than june, but by sep the novelty of summer wares off as people are back at work and school so they think it should be getting cold and horrible just cos it gets darker a bit earlier, when in fact sep rarely feels cool to me as many days are about 18-19c the same as june in most years, same example for april and october, there is more chance of frost in april than october but as it gets dark earlier in oct people think october is colder