Heat waves explained: How temperatures are rising, breaking records in the US

Last week, 227 US records were broken for highest temperature for particular days.

Sweltering temperatures flirting with 37 degree Celsius blistered parts of the US Midwest and East Coast and sizzled through the Independence Day holiday last week, leaving one dead in California as massive fires forced hundreds to evacuate.

"Large fire activity is spread across the country from Florida to Alaska," the National Interagency Fire Center announced, as temperatures spiked above 40 degrees Celsius in some places.

Over 113 million Americans are under heat warnings or advisories stretching from the Mississippi Valley, up to Philadelphia, Chicago and bending over to New York, Boston, Baltimore and Washington DC, said meteorologist Patrick Burke. Record high temperatures have been logged over the past week not only in the US, but around the world.

Here's a quick look at what's going on.

Why is this news?

For the past week through Tuesday, 227 US records were broken for highest temperature for particular days, and another 157 were tied, federal statistics show.

There was also a lack of cooling overnight, with 451 records broken for warmest minimum temperatures for particular days, and another 421 tied. In Burlington, Vermont, for example, the temperature got down only to 27 degrees Celsius on 2 July, its highest low temperature ever.

Record high temperatures have been recorded over the past week in the U.S. and elsewhere. AP

Record high temperatures have been recorded over the past week in the U.S. and elsewhere. AP

Some other countries have seen all-time highs, such as 41 C in Tblisi, the capital of the nation of Georgia, on Wednesday, and 43 C in Baku, the capital of Azerbaijan, on Sunday. On Monday, Iran experienced its hottest July temperature ever, 53 C.

Is climate change to blame?

Heat waves are a part of every summer, and scientists hesitate to link any single weather event to the warming climate that researchers have measured over long periods of time. Still, Matthew Rosencrans of the National Weather Service says that because of global warming: "Heat waves like this are likely to be more frequent going forward than they have been in the past."

Jeff Masters, director of meteorology for the private forecasting service Weather Underground, said the past week's heat wave "is the kind of thing you expect to see on a warming planet... it's easier to set a heat record." He notes that 2016 was the warmest year on record globally, and that year saw the most all-time heat records broken around the world.

Any relief in sight?

In the US, Masters said, a cold front should bring relief from the heat and humidity in the Midwest and Northeast on Friday through Sunday. Southern California will get severe heat during that time, he said, with a high of 39 C forecast for Friday in Los Angeles. That city has experienced only five July days in recorded history that were warmer, he said.

The coming week will be pretty hot over most of the US, especially in the West, forecasters say. For the last two weeks of July, temperatures over the eastern half of the country are likely to be closer to average than they were this past week, while probably remaining above average in the western part of the country and the southern Plains.

With inputs from agencies

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