I don't remember where I saw this. One of the threeper/prepper sites. My apologies for not giving credit but this has been sitting as an open tab for over a week waiting for me to have time to put a link to it.
Here are solar flare HF propagation charts useful to HAM radio enthusiasts. When the solar flares are in season, radios can reach farther. (That's the simple answer anyway). Not just HAM radios either. During the CB radio fad in the 1970's there was a solar flare season, and the fad faded with the season. Solar flares are on a 11 year cycle, and they were supposed to be at their peak in 2012-2013.
This solar flare stuff is something I have to learn about. I'm still pretty much a n00b, but a n00b can still link to something useful.
Public announcments from the near future
1 hour ago