Thermals

Monitor your device's thermal state and heat-related constraints.

iPhoneiPadMacApple Vision ProApple TVApple Watch

Thermals: live thermal state with a gauge and recommendations

Overview

The Thermals tool helps you understand when your device is getting hot and whether iOS is applying thermal limits that can reduce performance.

Table of Contents

• Overview
• Main Sections
• Thermal States
• Notes And Limitations

Main Sections

Thermals is a single scrolling screen with:

• A hero gauge that visualizes the current thermal state and a percentage-style level.
• A thermal stack that highlights the current state across Nominal, Fair, Serious, and Critical.
• A Current State card.
• A Recommendation card with guidance based on the current thermal state.

Details and recommendations update with thermal state

Thermals is a single screen you can scroll

Thermal States

Lirum uses iOS thermal states, each with a color and icon:

State	Color	Icon	Gauge Level
Nominal	Green	Checkmark	0%
Fair	Yellow	Warning triangle	33%
Serious	Orange	Flame	67%
Critical	Red	Exclamation octagon	100%

The animated background gradient shifts to match the current state color.

The thermal stack shows all four states and uses a cascade effect -- all states up to and including the current level are lit. For example, if the state is Serious, then Nominal, Fair, and Serious segments are all filled.

Lirum records a state history of thermal state transitions with timestamps (up to 100 entries), letting you track how the thermal state has changed over time.

What You Can See

• Thermal state (for example: nominal, fair, serious, critical)
• Indicators that performance may be reduced due to heat (device/OS dependent)
• Related context from other tools (CPU usage, charging, background activity)

Notes

• Available thermal details vary by device model and iOS version.
• Sustained high CPU/GPU load, charging, direct sunlight, and poor ventilation can trigger thermal limits.

Notes And Limitations

• On iOS/iPadOS the tool reports the system thermal state (Nominal/Fair/Serious/Critical), not a physical temperature reading. On macOS Catalyst it additionally reads and displays real hardware temperature sensor readings -- per-sensor °C values, an average temperature, and the hottest sensor.