I lived in the Middle East for 12 years. The law was if the temperature went above 45 C workers had to be sent home. The temperature was determined by an official government thermometer. Never once, in my 12 years, did the government's temperature reading reach 45 C - but at home and at work we saw temperatures as high as 49 C. I never saw the magic 50 C reached but people reckon it had done in the past.
I used to remove my tie and roll my sleeves up when the temperature reached 40 C. At 45 C I would take my socks off and wring them out.