Check temperature of Raspberry Pi CPU

The vcgencmd utility allows reading a few dozen hardware measurements on the Raspberry Pi boards.

CPU Temperature is checked by:

vcgencmd measure_temp

Typical temperatures in office environment, with case:

Pi Model heatsink usage temp [C]
2B yes light-moderate 40..45
4B no light-moderate 65..70
4B no YouTube 720p60 85

A red thermometer icon GPU-superimposed on the Raspberry Pi display output means the Raspberry Pi is overheating and is throttling the CPU and GPU to avoid self-destruction.

Raspberry Pi 0, 1, 2, 3 temperature thresholds:

CPU temp. [C] icon throttle
< 80 none none
80 - 85
half full thermometer red
CPU
> 85
full thermometer red
CPU & GPU

Raspberry Pi 4 temperature thresholds:

CPU temp. [C] icon throttle
80 - 85 none CPU: 1000 MHz
85 - 90
half full thermometer red
CPU
> 90
full thermometer red
CPU & GPU

The current Raspberry Pi CPU clock speed is obtained from

vcgencmd measure_clock arm

The output is in units of Hertz. The Raspberry Pi CPU clock speed and power consumption is dynamic:

clock speed [MHz] Raspi 2 Raspi 3 Raspi 3+ Raspi 4
idle 600 600 600 600
100% one or more cores 900 1200 1400 1500

Log temperature measurements with crontab -e. This can periodically log temperature and CPU frequency, e.g. add a line like:

@hourly  vcgencmd measure_temp | /usr/bin/logger

logger writes the measured parameters into the system log.

Related: Monitor Raspberry Pi DC input voltage