I have captured many swarms lately in thunderstorms. Not one swarm this year was taken during sunny weather. Of course this has been a bad and rainy year, but I wondered just what weather conditions others had when they captured swarms.
So far, that ratio for my swarm captures has been like this:
Sunny day: 0%
Cloudy day: 10%
Rain only: 39%
Tornado Warning: 1% (I did not know it until after I had taken the swarm!)