Fall is a wonderful time to visit the NFY. The weather is really pleasant; it is shirt-sleeve or light-fleece time...carry a packable wind/rain shell though. The water is low and absolute cystalline. It is no-hurry-up fly fishing; late mornings to late afternoon. "Prospecting"* with dry flies will produce feisty rainbows that aggressively inhale your #14-16 generic patterns.
During late-October evenings you'll witness flights of October Caddis...so a huge dry/small nymph dropper tandem is always a good ploy, even during the day. Best to look for shaded areas, aside rock-outcroppings and under stream-side vegetation if you do the daytime angling with the aforementioned rig.
*Speaking of "prospecting".....placer gold-mining is now officially illegal on the NFY. As anglers we no longer have to be vigilant about stepping into deceptively deeeeeep dredging holes. Another up-side is not rolling an ankle-leg-bone-busting-boulder; having become unstable from suctioning-out its underpinnings. Also the dredging equipment, floating sluice boxes and 8" flexible suction hoses will not be anchored on the water. But, still be conscious of tripping over cables and lines strewn about the defunct mining claims....sometimes hidden amongst the stream vegatation & rocks.