Phoenix will mark the 16th consecutive day of 110-degrees Saturday, putting it on track to top the longest measured stretch of such heat.

“This weekend there will be some of the most serious and hot conditions we’ve ever seen,” said David Hondula, Phoenix's chief heat officer.

“I think that it’s a time for maximum community vigilance.”

Temperatures on Friday in Phoenix hit 116 degrees by late afternoon and the National Weather Service has forecast record high temperatures for the next five days with highs up to 118.

That would shatter the longest 110-degree streak of 18 set in 1974.

The heat was expected to continue well into next week as a high pressure dome moves west from Texas.

Phoenix is an urban heat island where concrete, asphalt, steel and tall buildings constructed closely together result in heat accumulation. Because of this, temperatures don't drop quickly after the sun sets.

“It's important for the temperatures to go down at night to offer relief to people needing to recover from the daytime heat,” Sean Benedict, lead meteorologist with the National Weather Service in Phoenix, said.

Fueling the current heat wave is the delayed arrival of this year's monsoon rains. The season officially began on June 15.

The Associated Press contributed to this report.