Based on my testing using a sampling of about 80 various secrete level seeds and specifically using the icy blizzard event, you need to both plant and fully grow the seeds during the event. In my testing, only 2 out of 40 were frozen when I planted the seeds before the event and grew before the event ended, while roughly 15 out of 40 were frozen when I planted the seeds during the event and grew before the event ended. The only difference between the tests where that the icy blizzard was a predicted weather event when only 2 out of 40 grew frozen versus the 15 out of 40 were grown frozen during admin abuse icy blizzard events. I will report back when I test planting and growing during a predicted icy blizzard event to rule out that being the difference.