Body temperature rises in summer!

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It's about my wife. Her body temperature always rises upto 103 during summer mostly in hot days! She is 22, Her BP is only 90/50 and weight is 41 KG. She sweats less! Glucose or other cold liquids or paracetamol can't decrease her temperature that time. in this condition she feels headache, vomiting... after 1 hours again it comes to normal It is not related with her period/miens . it happens only on hot days. Is this a disease? is there any medicine of this problem? Can you help me!