I found a nice way to add the visuals from the BuienAlarm website: www.buienalarm.nl as a Panel Iframe to Home Assistant.

1. Download the file buienalarm.html to the directory config/www
2. Add the following to configuration.yaml:

panel_iframe:
  regen:
    title: Regen-voorspelling
    icon: mdi:weather-pouring
    url: /local/buienalarm.html

Result: When you have done this, you will see the default welcome-page. Enter/select your city and the prediction will be shown!