Mac thermal throttling: what the heat level means

Mac thermal throttling is macOS slowing the processor to bring its temperature down. macOS tracks a heat level in four steps, nominal, fair, serious and critical, and Apple’s developer documentation says performance is reduced at serious and significantly affected at critical. In Activity Monitor, kernel_task using a large share of the CPU is the sign Apple points to.

By the Scope teamUpdated October 18, 20267 min read

What do the Mac’s heat levels mean?

macOS reports one of four heat levels, which Apple calls thermal states. Apps can read the level, and macOS acts on it. Here’s what Apple’s developer documentation says about each:

Heat level	What Apple’s documentation says	What you might notice
Nominal	Within normal limits	Nothing
Fair	Slightly elevated; macOS runs the fans and stops background services that aren’t doing work you need right away	Fans start; background tasks wait
Serious	High; macOS takes moderate steps that reduce performance, and the fans run at maximum speed	Loud fans; heavy work takes longer
Critical	Significantly affecting performance; the Mac needs to cool down	A clearly slower Mac until it cools

So a Mac at nominal or fair isn’t throttling in any way you’d feel. Serious and critical are the levels where heat costs you speed.

Is my Mac throttling? How to check

Activity Monitor doesn’t show the heat level itself, but macOS leaves signs.

Open Activity Monitor. It’s in Applications > Utilities, or search for it with Spotlight.
Click CPU, then click the % CPU column heading to sort the list, busiest first.
Look for kernel_task. Apple says one of its jobs is to help manage the processor’s temperature, by making the CPU less available to processes using it intensely. When kernel_task shows a large percentage while your Mac works hard, macOS is holding back the heat.
Look at the app above it. That’s the work making the heat.

Activity Monitor's CPU list sorted by % CPU: Blender at 978.6%, Final Cut Pro at 96.4%, and kernel_task highlighted at 88.7% — Blender renders on every core, and kernel_task rises to keep the heat in check. Illustration with made-up readings.

Activity Monitor counts each processor core as 100%, so a busy app can show far more than 100%. kernel_task high CPU? Your Mac is cooling itself explains kernel_task in more detail.

You can also ask macOS directly. Open Terminal (in Applications > Utilities) and type:

pmset -g therm

Its manual page (man pmset) says this shows thermal conditions that affect CPU speed. It isn’t available on every Mac.

Your ears are a clue too. Apple says the fans run faster to provide more airflow, and in a warm room they turn on sooner and run faster. MacBook fan loud? What’s making it spin up covers that sound.

Why does a Mac throttle?

A Mac reaches the higher heat levels when it can’t shed heat as fast as it makes it:

Long, heavy work: renders, exports, games and big builds keep every core busy for minutes.
Blocked air: beds, pillows and laps cover the vents, and the fans can’t move enough air.
A warm room: Apple designs Mac laptops for rooms between 10 °C and 35 °C (50 °F and 95 °F), and warns against leaving one in a parked car.

Why is my MacBook getting hot? walks through each cause.

How do I stop my Mac from throttling?

Let the heavy job finish, or quit the app. Save your work first. If you don’t need it right now, quit it from its own menu.
Give it air. Use your Mac on a hard, flat surface, and keep the keyboard and vents uncovered.
Keep the room within range, 10 °C to 35 °C.
Install macOS updates. Apple lists this among its steps for a Mac laptop that runs warm.
On some Macs, choose High Power Mode for heavy work. Choose Apple menu > System Settings, click Battery, and under Energy Mode choose High Power from the On power adapter pop-up menu.

Battery in System Settings at 82%, with Energy Mode's On power adapter pop-up menu set to High Power — High Power on the charger, for long renders. Illustration with made-up readings.

Apple says High Power Mode lets the fans run at higher speeds, and the extra cooling may let the Mac perform better in very intensive work. You’ll hear more fan noise. It’s offered on MacBook Pro introduced in 2024 or later with a Pro or Max chip, MacBook Pro models from 2021 through 2023 with a Max chip, Mac mini introduced in 2024 or later with a Pro chip, and Mac Studio introduced in 2026. For the 14-inch MacBook Pro with M4 Pro or M5 Pro, Apple recommends its 96W USB-C Power Adapter for High Power Mode while charging.

If your Mac gets hot during light work, restart it. On a Mac laptop with Apple silicon, Apple also suggests closing and opening the lid. If it keeps happening, contact Apple or an Apple Authorized Service Provider.

Questions people also ask

Does thermal throttling damage a Mac?

Throttling itself is a protection, not a fault: Apple’s documentation describes the higher heat levels as steps macOS takes to bring the temperature down. Keeping your Mac in a room between 10 °C and 35 °C, with its vents clear, keeps it in the lower levels more often.

Do MacBook Pros throttle?

Any Mac can reach the higher heat levels during long, heavy work, especially in a warm room or on a soft surface. Some MacBook Pro models offer High Power Mode, which lets the fans run faster for very intensive work.

Can I see my Mac’s CPU temperature?

macOS doesn’t show chip temperatures. Apple says third-party apps that show temperatures don’t measure the case, which is much cooler, and that you should never use them to diagnose possible hardware issues.

Is Low Power Mode the same as throttling?

No. Low Power Mode is a setting you choose to reduce energy use, while the heat level is macOS responding to temperature. Low Power Mode on a Mac: what it changes explains the setting.

Scope for Mac · Free, coming to the Mac App Store

How Scope helps

Scope is a free Mac menu bar app that shows the heat level macOS reports, as Normal, Warm, High or Critical, beside how busy the processor is and which apps are using it. It shows macOS’s own heat level, not temperatures in degrees or fan speeds, so you can see when heat may be costing you speed without opening Terminal.

In your menu bar

Scope’s CPU · GPU · RAM panel, opened from the menu bar: CPU 86%, GPU 38%, RAM 62%, Thermals: High, and the tip “Your Mac is getting hot” — Scope sits in your menu bar, and one click opens its CPU · GPU · RAM panel.

The heat level, in plain words

Thermals sits beside the chip’s name, in macOS’s four levels: Normal is nominal, Warm is fair, High is serious and Critical is critical. At High or Critical, the levels where performance is reduced, Scope’s tip says your Mac is getting hot.

Scope’s CPU · GPU · RAM panel in a calm moment: CPU 34%, GPU 12%, RAM 62%, Thermals: Normal, and the tip “Short CPU spikes are normal” — A calm moment at Normal, and the render at High.

Scope’s CPU · GPU · RAM panel while Blender renders: CPU 86%, GPU 38%, RAM 62%, Thermals: High, and the tip “Your Mac is getting hot” — A calm moment at Normal, and the render at High.

How long it’s been working

CPU history keeps the last 10 minutes, so you can tell minutes of heavy work from a passing spike. Scope shows each app’s share of the whole processor: this Mac has 15 cores, so Blender’s 978.6% in Activity Monitor is 978.6 ÷ 15 = 65.2% here. Scope lists your own apps, not macOS processes such as kernel_task.

Scope’s CPU history over 10 minutes: around a third, then about 86% in the last few minutes — Minutes near 86%, with Blender at the top.

Top CPU processes in Scope: Blender 65.2%, Final Cut Pro 6.4%, Adobe Lightroom 2.8% — Minutes near 86%, with Blender at the top.

Told when heat lasts

Scope waits until macOS has reported high heat for at least 30 seconds, so a passing spike never raises an alert. Scope Free shows the alert when you open Scope. Scope Pro adds a red + on its menu bar icon and names the busiest app, with its helper processes counted together, and a tip about what it’s doing.

Scope shows and explains. It doesn’t quit apps, change Energy Mode or control the fans.

Scope Pro's alert "Your Mac is getting hot": macOS reported high heat for at least 30 seconds, and Blender is busiest now at 65% CPU, with its tip — Scope Pro When high heat lasts, Scope Pro names the app behind it.

Everything this part of Scope showsMac CPU, GPU and RAM monitor for your menu bar

Try it here

The real Scope, working, right in this page.

Click any item in the menu bar, or a card inside, as you would on your Mac.

Scope Pro Every menu bar item is shown here. Scope Free keeps one whole item of your choice, with every reading inside.

See your own Mac’s heat level.

Keep reading

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Low Power Mode on a Mac reduces energy use so the battery lasts longer. Here’s how to turn it on, what Apple says it changes, and when to use High Power.

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Sources

Last checked October 18, 2026. Readings, apps and files in the pictures are from a made-up Mac.