At the moment I have not tried 472kHz (630m) WSPR TX for a while as I need to replace the wire in my earth-electrode "antenna". In past winters I have had lots of fun overnight with low ERP WSPR. I really should try again during January, February and March.
I still have a quiet noise floor on 472kHz WSPR RX. With AM on 160m, 80, and 40m, the noise floor is S8. WSPR being a narrow-band mode seems to do much better.