If your CPU or Memory, while using WebStorm/PHPStorm, usually looks like this:

This is known issue, that users of JetBrains IDEs are faced with pretty often, usually on Linux.

The reason of this can be in OpenJDK that is used in Ubuntu by default:

You can try to install JDK from Oracle:

• I used this guide: https://askubuntu.com/questions/1287192/how-do-i-control-the-cpu-fan-speed-on-ubuntu-20-04

After that your CPU/Memory can relax: