"Bruce in Alaska" wrote

Paths go Stoned Dead for a few days untill the thermal Inversion
rebuilds. Path Studies that we did back then, showed that these things
were good for 60 to 70 days out of the 90 day Salmon Season, and that
justifdied using them, untill good phone service was established in the
region. Now they are just a cheap backup for commercial communications.

In really warm waters, the tropo-ducting is an annoyance that brings
unwanted radio traffic from hundreds of miles away, and it does this most
nights in the summertime.

http://www.iprimus.ca/~hepburnw/tropo_xxx.html

Find your ocean and see what the ducting forecast is.

Jack