When will it start to cool down in Arizona? Here's what the experts say

Metro Phoenix is breaking weather records as temperatures climb and the monsoon fails to bring rain.

Even when you're avoiding the hottest time of the day, relying heavily on your air conditioner and doing everything possible to stay cool, it's normal to start obsessively ruminating on when the misery will end.

Unfortunately, the high temperatures aren't expected to drop dramatically in the near future. Officials with the National Weather Service in Phoenix said highs were expected to hit 115-117 degrees until Friday when chances of rain return.

With that in mind, here's everything you need to know about when summer will end and it may finally cool down in Arizona.

Will it rain in metro Phoenix this week?

The hot weather was expected to continue, with temperatures hitting 115-116 degrees through Friday, according to Matt Salerno, a meteorologist with the National Weather Service in Phoenix.

However, metro Phoenix will see an "increase in moisture and a more favorable monsoon pattern" over the weekend, Salerno said.

Chances of rain were expected to increase on Friday, peaking at 30-40% on Saturday and Sunday, he said. The chances of rain would linger through the middle of next week, though south-central Arizona was most likely to see rain then.

"That will help to quell those really hot temperatures," Salerno said. "So, it will be hot but not as hot."

Temperatures were expected to drop to 105-109 degrees on Sunday, he added.

More:This simple tip could save you money on your electricity bill during hot Arizona summers

When will it start to cool down in Arizona?

With a late start for monsoons and a record-breaking heatwave ongoing almost all of July, this summer in Arizona has been brutal with residents craving an escape from the 115-degree days. 

This is an ongoing trend as Arizona summers often exceed 100 degrees with July and August being particularly hot. On brand with the nickname "Valley of the Sun," Arizona weather starts getting warm as soon as late May and grips on, not dipping into 90 degrees or lower until well into September or October. 

The National Weather Service forecasts that the average time Phoenix breaks into less than 100-degree weather is around Sept. 20.

When is the last day of summer?

The autumnal equinox marks the official start of fall. The equinox typically falls on Sept. 22 as it does this year, though it can fluctuate due to leap years.

On the equinox, the Earth's axis is tilted at the perfect angle to create nearly equal amounts of daylight and darkness at all latitudes, according to the National Weather Service. This is the astronomical start of the season. 

There's also the meteorological start of the season. This definition accounts for the annual changes in temperatures and the 12-month calendar, creating seasons that begin on the first day of a month and last for three months. Under this definition, summer ends on Aug. 31 and fall starts on Sept. 1, according to The Old Farmer’s Almanac.

Former Arizona Republic reporter Ellie Willard contributed to this article.