Major airlines delayed and cancelled flights out of Las Vegas and Phoenix airports as temperatures hit the high 40s, citing difficulty in operating aircraft in extreme heat - causing plenty of headaches for airlines and travellers alike.
States in the southwestern USA, such as Arizona, California, and Nevada are having one of their hottest summers on record.
Temperatures are expected to fall below the 100-degree mark after 8 p.m., so perhaps passengers will be able to travel beyond that.
The forecast called for a high of 120 degrees (49 degrees Celsius) in Phoenix, which it hasn't seen in more than two decades, and 126 in Death Valley.
Summer is rolling in hot with a heat wave expected through Thursday in Marin before it cools down for the weekend. "This is actually the peak of the heat that we're seeing in the desert Southwest, where we're talking all-time record highs that can be broken".
Searing footpaths are the bane of human and beast alike in Las Vegas.
The crippling heat wave drove residents, animals even air conditioners to the breaking point.
One person uses the CityScape splash pad to stay cool as temperatures climb to near-record highs in Phoenix on Tuesday.
Extreme heat on the ground also affects airport workers; loading and unloading luggage and servicing planes between flights could become more onerous.
It is sometimes more hard to get airplanes off the ground in extremely hot weather.
The National Weather Service has issued an "excessive heat warning", effective until Sunday evening local time, for south-central and southwest Arizona.
"We tend to ignore the atmosphere and just think that the plane is flying through empty space, but of course, it's not", said Paul D. Williams, a professor in the Department of Meteorology at the University of Reading in Britain who studies climate change and its effect on aviation.
Phoenix is the second-fastest warming city in the USA over the past 50 years while Las Vegas comes in at third and Tucson at seventh.
Sin City is sizzling in triple-digit heat this week.
Take the grounded flights, for example. One thing you might not expect is that they are handing out blankets. Hot air is less dense than cold air, and the hotter the temperature, the more speed a plane needs to lift off.
Annette Garcia, the shelter's rescue director, told NBC station KMIR of Palm Springs that staffers have to go stall by stall dropping blocks of ice in the horses' drinking water. That's now a rare occurrence. He works for the National Weather Service in Phoenix.
An American Eagle jet lands in Phoenix on Monday. There are far more serious impacts that will put more lives at risk if carbon pollution continues unchecked.
The study of almost 2000 deadly heat waves worldwide since 1980 was published Monday in the journal Nature Climate Change, a monthly peer-reviewed journal.
"People underestimate how that heat can get trapped within Phoenix, in areas such as Camelback Mountain, because there's not a lot of places for the heat to dissipate", she said.