Windows tray displaying temperature and humidity, possible?

There’s a Home assistant desktop app that has a tray icon: Home Assistant desktop app (Electron )

Unfortunately it has not been updated to work with the new authentication system and the author has not been seen for a year.

Then there’s this: Mqtt Control - small mqtt client service to connect my windows based pc to home assistant

No tray icon (i think) but it may suit your requirements.

Edit: no that last one is only good for controlling the PC and displaying the PC stats in HA.