[sukhavati]

I was trying to find stuff around Oct 2003 when the last event of this magnitude took place, but I wasn't able to find anything comparable. From what I can tell the forecast is more mild on the 12th UTC, so I wouldn't worry that much about that. I was worried in my case because my flight leaves pretty much at the apex of the geomagnetic storm.

I think we can expect delays, GPS being unresponsive, radio issues, and some control tower congestion & issues. Can't really comment with any more detail.

[skywal_l]

Looking at https://en.wikipedia.org/wiki/Solar_cycle_25 there's already been a G4 in march and it didn't seem to have caused any issues (AFAIK).

[sukhavati]

The March G4 was unexpected. I wouldn't be surprised if this one turns out to be much stronger than is modeled today as well.