TODAY   |  July 17, 2013

Massive heat wave bakes much of US

Forty-three states are experiencing temperatures in the 90s this week, and 16 have issued heat advisories or warnings. The heat is expected to break over the weekend. NBC’s Tom Costello reports and TODAY’s Al Roker gives the forecast.

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This content comes from Closed Captioning that was broadcast along with this program.

>> an oven in that stadium. let's get right to tom costello. he is sizzling away down in washington . tom, good morning to you.

>> reporter: good morning. already 81 degrees here in washington . at 7:00 we're headed to 97 degrees high humidity today. an orange air quality advisory. if you have asthma, they expect and they suggest you stay inside. this heat wave has a huge grip on much of the country and it's supposed to only get hotter. summertime and is living is anything but easy across much of the country. but for the pedal pushers in the big apple it's down right miserable.

>> it's very difficult because people have been scared of the weather. it's too hot for them.

>> reporter: it could be worse, like 120 degrees inside his office.

>> i have one fan here, one fan here.

>> reporter: the east coast baking in the 90s but oh the humidity. across the national mall , segway tour gay luide lee robinson is in the sun for 11 hour ace day. the segway breeze helps.

>> you have to drink a lot of water to keep up with it.

>> reporter: not enough of it for the 100,000 people in the washington suburb of prince george 's county. a water mane break is forcing mandatory restrictions.

>> i have two bottles. this is all that was left.

>> reporter: most of the country, 43 states in the 90s this week. 13 states issued heat advisories or warnings with heat indices at 105 in places. less time on the field and more h 20.

>> water breaks.

>> reporter: meanwhile at this nursery in maryland, christy carpenter and her crew spend 8 to 10 hours in the sun.

>> the heat is sticky. that's what d.c. heat is. it's sticky.

>> reporter: today we're expecting 140 million people across the country are going to be sweltering in 90 degree temperatures or above. as for those people in prince george 's county, they maybe without water until the weekend.

>>> thank you so much. for a second i thought he was going to say 140 degrees. it feels that way.

>> that's right. it almost feels like that. but we now have 16 states under heat add sivisories. this is expanding to the west. we normally don't see that. we do have a change coming so we're going to have to put up with this heat for another few days. washington d.c. will feel like 102. 97 in new york as you get into parts of new england. 101 degrees. as we move to the west, it's going to be like near 100 degrees. same thing in columbus ohio . green bay wisconsin 101 and further to the west, into the midwest we're in the plain states. temperatures again feeling like they're in the mid to upper 90s. the good news, here's the change coming. we're finally going to see the jet stream dip down on saturday. that means we're finally going to get cooler less humid air by sunday into the northeast. it gets in saturday as we get into the upper midwest with maybe severe weather coming along with that. savannah.