Legally, your dad's boss can be taken to court over that. The boss should be doing a risk assessment to decide whether its a health risk for his employees to continue working (obviously it is). At 58.4 degrees your dad is well within his rights to complain to either his boss or work cover, without losing his job.....
What he could do is complain he is feeling ill/sick/dizzy from the heat, then go to the docs and get a medical cert and a workcover cert to cover his absence at work.
don't quote me on this but i'm sure theres also a temperature put in place for any workshop to stop work if it gets over that certain temp....up here in Qld i'm sure its 42 degrees or something.