Seems like a feature gap, and one that wouldn't be too difficult to fill. I'm trying to tune my cooling and the SG-3100 is a device that I'd like to make sure I'm keeping very happy. Point-in-time data is only so useful toward that end.
Is there an active feature request (or current solutions) for integrating sensor / temperature data into the RRD graphs? How about in SNMP output? Temperature data is not available in either that I can see.
feature request: https://redmine.pfsense.org/issues/9297
You can also achieve this with telegraf and the exec plugin (sysctl)