Hi JCarlB,
Do you notice this behavior only on YouTube or other apps that stream video, or when playing games?
It can be expected for the iPhone to get a bit warmer while doing a more intensive task especially at higher brightnesses, however you can see tips for keeping your iPhone cool here: If your iPhone, iPad, or iPod touch gets too hot or too cold - Apple Support
"Your device might get warm
You might notice that your device feels warmer when you:
- Set up your device the first time
- Restore from a backup
- Wirelessly charge your device
- Use graphics-intensive or processor-intensive apps, games, or features, including augmented-reality apps
- Stream high-quality video
These conditions are normal, and your device will return to a regular temperature when the process is complete or when you finish your activity. If your device doesn't display a temperature warning, you can keep using your device.

If your device gets too warm
iOS and iPadOS devices have built-in protections to prevent overheating. If the interior temperature of your device exceeds the normal operating range, your device will protect its internal components by attempting to regulate its temperature. Here are some of the higher ambient-temperature conditions and activities to avoid, because they might cause your device to change performance and behavior:
- Avoid leaving your device in a car on a hot day.
- Avoid leaving your device in direct sunlight for an extended period of time.
- Avoid using certain features in hot conditions or direct sunlight for an extended period of time, such as GPS tracking or navigation in a car, playing a graphics-intensive game, or using augmented-reality apps.
If the interior temperature of your device exceeds the normal operating range, you might notice these changes:
- Charging, including wireless charging, slows or stops.
- The display dims or goes black.
- Cellular radios enter a low-power state. The signal might weaken during this time.
- The camera flash is temporarily disabled.
- Performance slows with graphics-intensive or augmented-reality apps or features.
Additionally, if you're navigating, your device might show this alert and turn off the display: "Temperature: iPhone needs to cool down." Navigation still provides audible turn-by-turn directions. When approaching a turn, the display will illuminate to guide you through the turn"
If you do believe the heat is excessive or notice alerts that the iPhone has gotten too warm and needs to cool down, contact Apple Support directly for additional assistance.
Take care.