From Hannah:

Maybe not a bug because I think it happens due to not being logged in, but..

When I get the email my starter is ripe and click the "click here to check on <starters name>s progress"

I then get a summary page. "Average Temperature" is shown as Fahrenheit here despite me having it set to Celcius when I log in.

Perhaps a feature request to have that toggle per starter on their public pages? 🙂