Forwarding from https://bugs.launchpad.net/ubuntu/+source/smartmontools/+bug/1653560
syslog entries like
Jan 2 20:22:27 server smartd: Device: /dev/sda [SAT], SMART Usage Attribute: 194 Temperature_Celsius changed from 110 to 112
should be less confusing and logging should by default only take place if something is worth to be warned about.
That said, a "health" value below 100% (e.g. 98%) should trigger the logging, because then the health status as specified by the vendor is no more perfect.
And the output could be more verbose and less confusing. I suggest:
Jan 2 20:22:27 server smartd: Device: /dev/sda [SAT], SMART Usage Attribute: 194 Temperature_Celsius: Thermal health changed from 110% (40°C) to 112% (38°C)
Given that normalization is specified by vendors, smartmontools could also take into account that e.g. health below 90% is critical (for WD drives that would be 60°C) and also should reported as critical (WARNING, etc.).
Eventually, this is not the right project. If so, please ignore this bug report (close/won't fix).
I filed a new issue at https://www.smartmontools.org/ticket/788 because I think that this issue should go there.
smartmontools won't fix this. If this can be fixed here, please leave this issue open.