Fall began on Sunday, but brought more record-breaking temperatures to the valley. With Wednesday's high of 113 degrees, it was the last 110-degree day on record, surpassing the record high of 108 set in 1989.

And according to the National Weather Service in Phoenix, the heat isn't expected to let up anytime soon. Temperatures are expected to reach 110 degrees by the weekend.

As residents wait to see what next week will bring, here's everything you need to know about what the weather is typically like and when it typically cools down in the Phoenix metro area.

When does it cool down in the Phoenix metropolitan area?

Nicknamed the “Valley of the Sun,” Arizona's weather begins to warm as early as late May and continues, dipping to 90 degrees or lower until well into September or October.

The National Weather Service predicts that the average day for Phoenix to drop below 100 degrees is September 29th.

The normal high for September 1st is 104 degrees, but this drops to 96 degrees by the end of the month. In October, average temperatures drop from 95 degrees at the start of the month to 83 degrees by Halloween. By the end of November, normal temperatures are 70 degrees.

This is the weather you can expect in the Phoenix metropolitan area

A look at how the Phoenix Zoo protects its animals from the heat

Zookeepers Stevie Merner and Ryan Vittetoe talk about keeping the greater rhino and the hornbill, a tropical bird, cool in the summer.

After the hottest summer on record, last week's highs in the 90s were a welcome, if temporary, reprieve. But the National Weather Service is forecasting daytime highs of over 110 degrees through Sunday in an unexpected fall heat wave.

“We have a really unusually strong high pressure system overhead,” said Katherine Berislavich, a meteorologist with the National Weather Service Phoenix. “It is currently focused just east over Colorado, but the center of this system will move back west and be overhead by the end of this week and into the weekend.”

A high-pressure system, sometimes called a heat dome, occurs when air descends from the atmosphere and compresses toward the ground. As the air sinks, it becomes hotter, clouds become smothered, and solar radiation increases.

Berislavich expects the hottest temperatures from the high pressure system to reach Phoenix on Friday and Saturday.

Next week it will cool down a bit but still reach triple digits. Temperatures will continue to be around 110 degrees to start the week but should moderate towards the end of the week.

Average temperatures for Phoenix

As fall slowly winds down in the Phoenix metropolitan area, here are the average high and low temperatures you can expect for the rest of the year, according to U.S. climate data.

• September: Average maximum temperature of 100 degrees, average low temperature of 77 Degree.
• October: Average maximum temperature of 89 degrees, average low temperature of 65 Degree.
• November: Average maximum temperature of 76 degrees, average low temperature of 53 Degree.
• December: Average maximum temperature of 66 degrees, average low temperature of 45 Degree.