On some lakes, the spawn can start real fast on a warming trend. It really does help if it's around a full moon. Some say a new moon, but I haven' paid enough attention to that to be sure.
I think in the spring, if you have a the water quickly warming on a good weather trend around a full moon especially, you'll have some bass making beds. I've seen them bed on some lakes every year in water still in the 50's. I see bass all over the state on beds in water in the high 50 to mid-60s.
I think some bass just spawn more for the time of year and weather trend than just purely based on water temperature. I've just seen too many bass on beds in water much colder than you read about over the years here in the Northern states. The really big move to beds might occur more around the expected temperature possibly, but I sure do see a lot of exceptions in both largemouths and smallmouths.
There have been a few biologists over the years who talk about a 'false' spawn in the fall, but it doesn't seem to be taken real seriously by many. Bass are pretty much creatures of their environment and don't have a big brain (we just sometimes think they're smarter than they are ).
I stopped at a Northern Michigan smallmouth lake one year in late September and found a small number of smallies in pairs making what looked like beds in the same reeds they spawn in during the spring. It sure looked like they were bedding. I don't know. I didn't go back up there to see what was going on later, but there are so many exceptions to the rule out there, it's sometimes hard to tell what is the rule.
There are bass in some lakes with consistent, moderate weather down South that spawn over an incredibly long period of time. Bass really don't get studied a whole lot up here. There's probably a lot of interesting things that might be learned, especially from one population to another. I don't feel real bad they aren't studied as much as other fish. They really do do a good job of taking care of themselves if we take care of the environment.