If your iPhone gets unusually warm and starts lagging during video calls when you're using mobile data, you’re not imagining it. This happens fairly often, especially during longer FaceTime, WhatsApp, or Zoom calls outside Wi-Fi coverage. The good news is that it’s usually not a hardware failure.
Quick answer: overheating during cellular video calls is typically caused by the modem working harder to maintain signal while the processor handles video encoding. Reducing network strain and background activity usually fixes it.
Why it Happens
Video calls already demand a lot from the phone. The camera, microphone, screen, and processor are all active at once. When you switch to cellular data, another heavy task is added: the cellular modem continuously boosts power to keep a stable connection, especially in areas with weak or fluctuating signal.
Heat builds up quickly under three common conditions:
- Poor or inconsistent cellular signal
- 5G connections constantly switching bands
- Apps running in the background using data or location services
Once temperature rises, iOS automatically slows performance to protect internal components. That’s why video may stutter, brightness dims, or the phone feels sluggish.
Fixes That Usually Work
Switch 5G to LTE Temporarily
5G can be faster, but it also consumes more power when signal quality isn’t strong.
- Open Settings.
- Tap Cellular → Cellular Data Options.
- Select Voice & Data.
- Choose LTE.
Many users notice the phone runs noticeably cooler during long calls after this change.
Lower Video Call Load
You don’t always need maximum video quality.
- Turn off HD video inside the calling app if available.
- Reduce screen brightness manually instead of leaving Auto-Brightness at maximum.
- Avoid Picture-in-Picture or multitasking during calls.
These small reductions ease processor usage immediately.
Close Background Apps Using Data
Streaming apps, cloud backups, and social media syncing can quietly compete for bandwidth.
- Open the app switcher.
- Swipe away apps you don’t need.
- Pause uploads or downloads before starting a call.
This reduces modem workload, which directly lowers heat.
Check Signal Strength Before Starting Long Calls
If you’re in a low-signal area, the phone increases transmission power constantly. Moving even a few meters — closer to a window or outdoors — can stabilize the connection and reduce heat generation.
Remove the Case During Long Calls
Some protective cases trap heat. Taking the case off during extended video calls allows passive cooling and prevents thermal throttling.
Update iOS
Apple regularly adjusts modem and thermal management behavior.
- Go to Settings → General → Software Update.
- Install any available update.
Several updates quietly improve how the device handles sustained network activity.
One Practical Habit That Helps
If you regularly make long video calls on cellular data, start the call with Low Power Mode enabled. It slightly limits background processes and prevents unnecessary performance spikes without affecting call stability.
Once the phone stays cooler, performance drops usually disappear on their own, and calls remain smooth even over mobile data.