As the Category 5 Hurricane Irma batters the Caribbean and moves on a path that could potentially affect Southern Florida, a free app that turns the iPhone to a walkie-talkie has climbed the charts of Apple's App Store due to its usefulness as a method of instant communication.

The app, called Zello Walkie Talkie, allows users' phones with a network or Wi-Fi connection to communicate as a two-way radio. This enables users to have immediate voice communication with other people on the shared channel, instead of having to place a phone call and wait for someone on the other end to pick up.

The free app proved useful for residents affected by the recent Hurricane Harvey which caused heavy damage to the Houston metropolitan area two weeks ago. It started rising in the charts when the hurricane made its landfall in Texas, and became a go-to app for Houston rescue workers.

As storm victims sought relief during Hurricane Harvey's aftermath, Zello has provided assistance. This is all thanks to dozens of channels popping up on the app, like Texas Search and Rescue, Houston-area midwives, and the Cajun Navy rescue volunteers.

"Many of us have friends and family in Houston," said Zello Chief Executive Officer Bill Moore to USA Today. "More broadly, technology like Zello allows people to solve things closer to the problem, where it's so effective."

With the people in the southeastern part of the country preparing for Irma's arrival and potential landfall, the app has skyrocketed to the top of the free apps chart in the App Store. According to the company's official Facebook page, Zello is seeing as many as 7,000 new registrations per minute. The company is doing great effort to maintain the software's uptime as more and more users sign up for the service.

Hurricane Irma is predicted to hit Southern Florida during the weekend.