Yes. We define heat stroke as a combination of hyperthermia ( 41°C, though can present with lower temperatures), often with loss of the capacity to dissipate heat and CNS impairment. Loss of ability to sweat is often a late and ominous sign. Don t sit in the sin for that long again. You can go into shock. Always keep hydrated and try to avoid exercise in the heat (direct sun). If you are shaking and feeling cold but hot on the outside, it s best you consult a Doctor. Ring NHS Direct on 0845 4647