iPhone heating up when outside.

Well, at 110-115, you are trying to operate your phone outside of its temperature range .. .especially if you have it in a protective case. Sorry, but folks living in the other extremes of severe cold weather face the same types of challenges using electronic equipment.

Environmental Requirements

• Operating ambient temperature: 32° to 95° F (0° to 35° C)
• Nonoperating temperature: −4° to 113° F (−20° to 45° C)
• Relative humidity: 5% to 95% noncondensing
• Operating altitude: tested up to 10,000 feet (3000 m)

Your phone will heat up if you are connected to a weak cellular signal, as 1 bar requires 10 times as much energy as full bars. And If you are connected to a 5G network 5G uses much more energy than LTE. The upper safe temperature for an iPhone is $35ºC, which is less than 110ºF, so you need to find a way to keep it cooler. I imagine you keep yourself cooler than 110º for your own health, so you need to treat the phone the same way you take care of yourself.