While Andy Williams might argue with me, I think early autumn is the most wonderful time of the year.
Where I live in Utah, there are all sorts of trees covering the mountains, so they are spectacularly multicolored come late September/early October.
Here are some other things I love about this time of year:
Footall season (Go Broncos!)
Seasonal foods and drinks like soup, pumpkin rolls, spice cake (with cream cheese frosting), red wine, and hot tea
Fall fashion (especially boots)
Halloween (costumes and candy, what's not to love?)
Warm days, chilly nights (perfect for snuggling up with someone you love)