Done 120 in Phoenix. Done negative 38 on jobsites in montana. Id argue heating is essential in this world. AC is not. Hydration and salt will replenish fluids lost.  Heat... yeah that's a little more tricky. -38 I did with a heated jacket for a day. And still tried to get back in the building and propane heaters.  Either way.  I get paid. And I'd rather just be outside reading a book and drinking a beer than be inside in climate control.