A heat wave in the Southwest United States has resulted in at least two deaths and has even forced a plane to return to its origin airport due to the extreme temperatures.

The National Weather Service is reporting 17 daily heat records were broken Sunday, but the peak of the heat wave will come Monday as temperatures in some desert area are expected to reach around 120 degrees.

Officials confirmed Monday that two hikers had died from heat-related issues in separate incidents on Sunday. The first victim was a 19-year-old woman who died on a trail near Tucson, Arizona, and the other was a man found a short distance away. There is also another person missing who was hiking on the same trail.

In addition, the extreme heat forced a United Airlines flight from Houston to Phoenix to return to Texas when temperatures reached 118 degrees in Arizona. The airline said it would compensate passengers and provide an added flight Monday morning.

For tourists making their way to the Southwest for summer vacation, the National Weather Service has issued excessive heat warnings for cities such as Tucson and Yuma, as well as popular destinations such as the Grand Canyon and Lake Havasu.