For those with questions regarding trend yields, applicability, and confidence in them, I urge you to look at some of the work done by the University of Illinois...the FarmDoc crew has studied this quite a bit....I believe Darrel Good started it while he was at UIUC, and Scott Irwin has lead the group since. https://farmdocdaily.illinois.edu/2020/06/unconditional-vs-condition...
The R2 at .91 is a strong indicator....well beyond just random chance
And it is more than just weather reflected in the gains....huge gains due to technology
There is a whole group of these articles discussing different variables....may be worth reading
have a great day.