Rated 5 out of 5 stars

Thanks for the work around!

Install the addon-bar first;
https://addons.mozilla.org/en-US/firefox/addon/the-addon-bar
I used the add-on manager to do this.

Install Forecastfox version 2.2.4 from this link:
https://static.getforecastfox.com/downloads/forecastfoxlatest.xpi