"Heat-related illness such as heat exhaustion or heat stroke are a real threat, " the National Weather Service said in issuing an excessive heat warning through Sunday for eastern Missouri, including St.

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The swimmer, Mohammad Alirezaei, did not compete in the men's 100-meter breaststroke heat Saturday because of illness and not for any other reason, a spokesman for the Iranian Embassy in Beijing told CNN.

CNN: Iranian swimmer quits Olympic race against Israeli

It is reached when heat is so severe that illness and death may occur among the fit and healthy, and not just in high-risk groups.

BBC: Storms lash UK while SE sizzles