One could argue that there's a certain "fading glory" concept in early D&D that seems to suggest the "feel" of Autumn. Elmore picked that up in his paintings by depicting them taking place in fall. Basically, I guess I'm saying that classic D&D had a Dark Ages feel to it that was evocative of "Fall."
Regarding the Lord of the Rings, I'm quite certain Tolkien's choice of seasons was very intentional and symbolic. Sauron's rise was like the world entering a long winter. When Aragorn was crowned, it was coming out of it. Yes, it took a YEAR (or was it close to two?), but who remembers that part? IIRC, the reason Frodo's wound pained him outside Mordor is because it was the ANNIVERSARY of his wounding on Weathertop. Likewise, the flowering of the White Tree was VERY intentional symbolism. Many magical realms from myth and legend (and fantasy) experience "perpetual summer" or "perpetual spring." For instance, Unseelie (the evil realm of Faerie) is often thought of as being in perpetual winter.
Seasons have a significance to them that seems to resonate within our consciousness. Even if you don't live someplace where you've experienced "real seasons" (as I don't), you still get it.
I think George Martin puts it best. Basically, in the standard premise of early D&D...
"Winter is Coming."
If that doesn't imply fall, I don't know what does.