"And i think i read somewhere that any fasting missed, must be added to the end of Ramadan, but how, he will still be working outside in the heat ?"

MR. Paul, that is your misunderstanding. If someone missed fasting during ramadan due to some valuable reasons, he has to complete it before next year ramadan, not to the end of ramadan.....
Almighty Allah is merciful to His creations. So He better knows what is good and bad for them..Thus He provided the rules and regulations to the believers how to live in this life....