This is an actual situation we encountered. In spite of the distance - 18 km - and the fact that antennas were not pointing towards each other, we still had extreme strong signals. At our receiving antenna the calculated difference between signal and our receiver noise floor was around 100 dB.
Other examples may give other signal values - but there is no need to go for extremes. A 100 dB difference is difficult enough to handle, but not impossible.
Calculation is based on free space attenuation - being on a hill we have clear line-of-sight. Receiver noise level based on a noise temperature of 290K is -174dBm/Hz or -140dBm in 2,5 kHz (SSB) bandwidth. This is 101 dB below the -39 dBm from the strong local.
The difference between a noisy and a noise free transmitter 20 kHz away from a weak station.