A punishing heat-wave has settled over central and eastern parts of the United States, pushing temperatures as high as 37degree Celsius and causing more than 22 deaths. The National Weather Service has warned of dangerous levels of heat and humidity creeping east, with no relief expected until Sunday. Officials said as much as 50 per cent of the US population was under a heat advisory. Yesterday, many regions in the central US and parts of the eastern seaboard also saw heat indexes – a combination of temperature and humidity – topping 43 degree Celsius.