Single digits, 100%.
Single digits range from -9F to 9F. Triple digits start at 100F, and can go way the fuck up from there. (And with climate change, they will!) Once you start approaching triple digits, you have to worry about humidity, because you can easily hit a combination that's literally too hot to live.
Is -9F unpleasant? Sure. But you can layer clothing, and that will keep you comfortable. Death Valley has hit >130F, and when that happens people die, even if they drink gallons of water and stay in the shade.
Right, but you're also creating a prisoner's dilemma. That is, if everyone agrees to work one way, and you have one person that breaks rules in a way that gets them ahead--and lets say that, in a purely communist society, that 'getting ahead' in this instance means that they need to put in less work to have the same result as everyone else, and thus have more time available for themselves--then it creates a strong incentive for everyone to follow suit. You need those outside regulatory bodies with enforcement powers in order to create the disincentive to breaking rules and agreements.
Perversely, farmers often know that what they're doing is deeply harmful for the environment, but there are strong financial disincentives preventing them from changing. Without both a regulatory structure forcing change on everyone, combined with incentives that make changing affordable to them (such as giving them cash to buy updated equipment to farm in new ways, and ensuring revenue levels), they're kinda fucked.