Washington, June 20 : More than 35 million people in multiple across southern US states, including Texas, Louisiana and Florida, are experiencing a brutal heat wave that is expected to last for days, according to the National Weather Service (NWS). A blistering heat wave will persist all this week, NWS said in its latest forecast late Monday. Thunderstorms, some severe, and heavy rainfall are possible in the next few days across the Southeast. Critical fire weather conditions persist in the Southwest, Xinhua news agency quoted the NWS as saying. Amid the sweltering heat, over 49,000 people in Mississippi, nearly 187,000 in Oklahoma, almost 79,000 in Texas and some 69,000 in Louisiana were left without electricity as of Monday evening, according to utility tracker poweroutage.us. While in New Mexico firefighters are battling a large fire, Phoenix, the state capital of Arizona, on June 18 recorded its hottest temperature of the year so far at 42 degrees Celsius. Heat waves are occurring more often than they used to in major cities across the US. Their frequency has increased steadily, from an average of two heat waves per year during the 1960s to six per year during the 2010s and 2020s, according to the US Environmental Protection Agency. /IANS