"A heatwave scorching parts of the US has surprised meteorologists as it moves east to west, something that rarely happens."
Via news.sky.com, 19 July 2013 - Millions of Americans are suffering another unbearably hot day from the East Coast to the Midwest.
The National Weather Service has issued heat advisories and warnings for several cities as the heat index - a measure of how hot it feels when relative humidity is factored in with air temperature - topped 100F (38C) earlier this week.
With many as those warnings still in place, temperatures are expected to range from 99F (37C) in Boston to 95F (35C) in Chicago.
New York City had a forecast high of 99F, with the hot streak expected to break on Sunday.
Thunderstorms are expected to bring some relief this weekend.
A bear cub and a lion get an iced treat at Chicago Zoo
The oppressively hot weather in the Northeast has surprised meteorologists because it is moving backward across America.
Normally US weather systems move west to east.
The western Atlantic high pressure system behind the hot dry weather started moving east to west last week and by Tuesday was centred over lower Michigan, said Jon Gottschalck, the operations chief at the National Weather Service's prediction branch.
"It's definitely unusual and going the wrong way," Mr Gottschalck told the AP news agency.
"This is pretty rare."
The National Weather Service has warned of the dangers of heat-related illnesses, asking area residents to be on the lookout for signs of fatigue, sunstroke, muscle cramps and heat exhaustion.
Temperatures are expected to reach 99F in New York City
Power grid operators are asking consumers to cut back as much as possible, as the heat wave drives near-record demand for power.
In California, 3,000 firefighters are battling raging wildfire near Palm Springs.