(CNN) -- Hamburgers and hot dogs weren't the only things sizzling this Fourth of July.
This time of year, triple-digit temperatures are the norm in the Southwest. And people in Arizona, Nevada and parts of California who celebrated America's 237th birthday weren't let down on Thursday: Highs went well past 100, as they have for the past week and then some.
But the Northeast? That part of the U.S.A. has been in a seemingly endless rinse cycle for much of the past two weeks, beset by rainy day after rainy day.
Those rain clouds, though, took a holiday on Thursday. The sun came out and so did the heat. The National Weather Service issued heat advisories through Thursday night for parts of four New England states because heat indexes -- how hot it feels, accounting for humidity -- reached or surpassed 100 degrees.
Those conditions became an issue on Boston's Esplanade, which is along the Charles River across from Cambridge and the site of the city's hallmark July 4th Boston Pops concert and fireworks show.
Before 6 p.m. some 120 people had already sought assistance, treatment or evaluation from medical personnel along the Esplanade, said Boston Emergency Medical Services Chief James Hooley.
The first person seeking help at one of the seven medical tents being run by EMTs and paramedics came in around 10 a.m., Hooley said. Four people in for heat-related ailments were sent to a local hospital out of abundance of caution, he added.
The Northeast could be sweating for a little while longer. New York City, for instance, is under a heat advisory through Saturday. The combination of high temperatures and high humidity will make it feel like it's 95 degrees, which can be dangerous in urban locales that don't have air conditioning.
"Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun and check up on relatives and neighbors," the weather service says.
The Northeast will be relatively cool compared with what the Southwest has ahead of it. Highs in Las Vegas are not expected to drop below 108 all week (though that's still cooler than Thursday). Phoenix will see similarly sweltering conditions, though there's a "slight chance of showers and thunderstorms" -- a rarity in these parts -- in the middle of next week, according to the National Weather Service.
From torrential rains to dangerous droughts
Folks in the Southeast and the Ohio River Valley know a thing or two about showers and thunderstorms. They got soaked by them all Independence Day, and those wet conditions could persist.
Flood watches are in effect from northern Ohio south to Alabama and extend east into states like West Virginia, the Carolinas and most of Georgia. They extend through Friday, if not longer, in areas that have already experienced days of soaking.
The wet stuff has prompted communities from Grove City, Ohio, to Franklin, Tennessee, to Decatur, Georgia, to postpone their July 4 celebrations, fireworks and all.
But some didn't let rain, rain and more rain deter them.
Georgia's capital should get 3 to 4 inches of rain by the time this weekend's over, according to CNN meteorologist Pedram Javaheri.
While much of the Peach State had been mired in drought for years, that's not the case this year thanks to months like the last one, when about 10 inches of rain made it Atlanta's fourth wettest June ever, said Javaheri.
Extreme to exceptional drought conditions persist east of the Mississippi River, according to the U.S. Drought Monitor, which is a partnership of the University of Nebraska's National Drought Mitigation Center, the U.S. Department of Agriculture and the National Oceanic and Atmospheric Administration.
The worst conditions hold in parts of Texas, Oklahoma, Nebraska, New Mexico, Nevada and Arizona.
The latter is the site of the Yarnell Hill Fire about 75 miles northwest of Phoenix, where 19 firefighters died this week trying to curb the blaze.
Mother Nature hasn't been cooperating, with temperatures soaring into the high 90s and winds gusting stronger than 20 mph once again Thursday.
But there could be good news coming, at least: The thermostat is forecast to peak in the 80s through the weekend. And there's a 10% to 30% chance of showers and thunderstorms over that stretch -- though lightning from those storms could spark yet more fires.
CNN's Ed Payne, Tina Burnside, Michael Martinez and CNN meteorologist Chad Myers contributed to this report.