The hay that a lad made locally in May which is the subject of another thread hasnt caught fire yet but he did spread it out in under cover!
Ouch! Done that in the past... I remember using AddH when we did little bales which was some rum stuff and would allow some heating but killed the mould spores. I used to stack the bales with horizontal vents every other course in the barn which helped a lot. However, big round bales killed that Two weeks "resting" worked wonders on a bit of green hay, and of course, it was a great walk with the kids of an evening, rolling the bales 1/4 turn, to stop the ground giving a damp patch on the bale!
Haylage was the secret for us, albeit plastic film is now getting less appealing. But in a season like this, it is a huge benefit to be able to wrap headlands and under trees etc!