Realms of Light
Ruth, his electrolytes may be low (salt, sugar, potassium) from the relentless heat and perspiring them out of his body. That can make one extemely weak. He may also be suffering from dehydration.
When either of these conditions occur, the desire to eat diminishes, thereby making matters worse.
You've just weathered one of the worst storms of the century, and you and your Daddy will weather this one as well.
On closing this reply, I will spend some time in prayer that your father will be on the mend.
Love & healing prayers,