[RFI] Powerline Noise

[Kelly Johnson]

What does it usually mean if powerline noise slowly increases from S0
to about S6 in the middle of the hot day and goes back to S0 an hour
or two before sunset?  It seems to me that I remember hearing that
certain types of causes tend to make it occur only when it is hot or
only when it is dry/wet, etc.  The noise appears to be worst on 6
meters and decreases as frequency is decreased.