Collecting and comparing environmental data was the whole reason I started homeassistant. I mostly use indoor sensors and compare with national weather service for outdoor, but I like seeing the data. Graphs of indoor/outdoor, next to https://cdn.star.nesdis.noaa.gov/GOES16/ABI/SECTOR/se/GEOCOLOR/600x600.jpg (which updates every 5 minutes) I live in the US Southeast, and the indoor/outdoor comparison, especially dewpoint, lets me know when it's ok to open windows overnight. i.e.: the overnight temperature usually drops below the A/C set point, but if that's going to draw in a bunch of humid air, it may feel more comfortable to keep the warmer, drier air. Actual, local outdoor conditions would be even better, because we do get localized summer showers that really raise the humidity in very small areas, and the NWS data comes from an airport 5 miles away.

I'd love to have some motorized windows, or even blinds, for automation. Absent that, there's nothing super obvious to me to trigger off environmental data.