Millions of Americans across the South have been told to brace for a deadly heatwave that could shatter more than 90 high temperature records. 

Texas has been battling extreme heat for more than two weeks with daily high temperatures above 110 degrees. 

But the weather could get even hotter and expand to other areas this week including Florida, Louisiana, Mississippi and New Mexico.  

Temperatures could go above 100 degrees in multiple cities and the duration of the heatwave could add to its seriousness. 

The excessive heat brings fears that two-thirds of the US could suffer blackouts this summer due to an increased demand for air-conditioning, which requires huge amounts of electricity.

Millions of Americans across the South have been told to brace for a deadly heatwave that could shatter more than 90 high-temperature records 

Texas has been battling extreme heat for more than two weeks with daily high temperatures above 110 degrees Fahrenheit 

The weather could get even hotter and expand to other areas this week including Florida, Louisiana, Mississippi and New Mexico

The National Weather Service has issued a heat advisory and excessive heat warning to several states across the South. 

Nearly 40 million people from Alabama to Arizona are sweltering due to the heat wave, which is expected to last until the July 4 holiday weekend. 

It could result in more than 90 record-high temperatures being broken this weekend with the majority occurring between Wednesday and Friday across Texas, the Mississippi Valley and parts of Florida. 

It will continue to be warm overnight with another 180 record-warm low temperatures potentially broken in the next week. 

‘Many areas outside south and south-central Texas (will) experience their most significant heat of the season thus far,’ the Weather Prediction Center said.

‘There may be more danger than a typical heat event, due to the longevity of near-record or record high nighttime lows and elevated heat index readings.’ 

It comes as Texas has been battling an extreme heat wave where temperatures have come close to the state’s record of 120 degrees. 

Rio Grande Village recorded 119 degrees on Friday and is set to hit that again on Tuesday.

The widespread heat will affect the different regions in different ways ‘with higher air temperatures in the deserts and west Texas and lower air temperatures but higher humidity and heat indices in east Texas, both contributing to a significant risk of heat-related illnesses’, according to the Weather Prediction Center. 

The National Weather Service has issued a heat advisory and excessive heat warning to several states across the South 

Nearly 40 million people from Alabama to Arizona are sweltering due to the heat wave which is expected to last until the July 4 holiday weekend

Temperatures won’t cool down overnight and this can be extremely dangerous as heat stress continues to build up in bodies and can increase risk of heat related illnesses or death. Pictured: Florida’s outdoor workers demand protection against the extreme heat on June 21

The temperature in the deserts and west Texas are forecasted to reach above 110 degrees and the humidity on the east of the state will make the air feel warmer than 110 degrees. 

Some locations including Midland and Corpus Christi will feel like 120 degrees with Houston expected to feel like 115. 

The National Weather Service said highs from southeastern Arizona through southern New Mexico and into Texas will remain in the 100s on Tuesday. 

The heatwave is forecasted to spread northward into Central Plains and Missouri Valley with temperatures in the upper 90s and low 100 degrees on Wednesday. 

And temperatures in Florida will remain hot on Tuesday and Wednesday, with highs in the mid-90s and could break daily records. 

Weather historian Christopher C. Burt told CNN: ‘There’s no break. Looking at the models, this heat dome over Texas looks like it’s going to be persistent, shifting a little bit to the east or to the west from day to day, but I imagine it’s going to be just blazing for the rest of the month.’

The heat wave has already led to deaths in some areas.  

A 14-year-old boy died while hiking in Texas during the heatwave on Friday, where temperatures were 119 degrees Fahrenheit. 

He was at the Big Bend National Park when he became sick and lost consciousness and his stepfather, 31 rushed to get help but crashed his car and died.

A Texas mailman also collapsed and died in the front yard of a home while he was out on a delivery during the excessive heatwave on June 20. 

Temperatures won’t cool down overnight and this can be extremely dangerous as heat stress continues to build up in bodies and can increase the risk of heat related illnesses or death. 

A 14-year-old boy died while hiking on Big Bend National Park, in Texas during the heatwave on Friday where temperatures were 119 degrees Fahrenheit

United States Postal Service worker Eugene Gates Jr, 66, pictured with his wife Carla, was delivering post door to door in Lakewood, Dallas when he collapsed and died on Tuesday

There are also concerns that two-thirds of the US could suffer blackouts this summer due to skyrocketing demand for electricity with people turning on air-conditioning to stay cool. 

It will be a real test for the power grid’s ability to cope and officials have warned large parts of the country could be without electricity. 

‘Two-thirds of North America is at risk of energy shortfalls this summer during periods of extreme demand,’ the North American Energy Reliability Corporation (NERC) said last month.

It added the entire US west of the Mississippi River could suffer energy shortages during ‘extreme conditions’. 

Texas’ state utility operator ERCOT issued a Weather Watch until June 30 to warn residents of the high demand for electricity because of the high temperatures.

It said there was enough energy to meet the demand, but new records could be set for daily use during the rest of June.