After looking around, I see that github member p0akley seems to have identified an issue 5 days ago that matches this description. Following his instructions I was able to resolve the issue with my Pi 3.

Seems there is a small adjustment needed in the file:
modules/default/currentweather/currentweather.js

Link to explanation / resolution:
https://github.com/MichMich/MagicMirror/commit/25ddf2c65178e2b8afe0709b48d5d30054208c04