Heat wave death toll hits 22 in US

US: A searing heat wave brought summer misery to the American heartland, enveloping as many as 17 US states in oppressive temperatures and humidity likely to persist into next week.

A message advising people to limit outdoor activity is displayed on an electronic street sign on the R.L. Thornton Freeway during a prolonged heat wave in Dallas, the US

At least 22 people have died during the severe heat wave that has recently hit the central and eastern parts of the US, causing the temperatures to rise to 37C and 43C.

"Dangerous" levels of heat and humidity is moving eastward and will stay in eastern areas until next Sunday, the state-run BBC reported the US National Weather Service as saying on Thursday.

"This is an exceptionally strong ridge of high pressure that really has an exceptional scope and duration," said Eli Jacks, a meteorologist with the National Weather Service (NWS).