Or maybe "wet avalanche" as opposed to a "dry avalanche". The wet ones have more force but the dry ones are faster.
If I was looking for an indicator of warmth, I would look for the wet kind.
I do not know they following, it is just my speculation.
But wouldn't two different conditions, (one of which was a wise seed-start-time) only occur at the same time in areas where the general rate of change of spring temperature was similar?
My spring might be off-and-on, gradually, from February through May in some years, or March through June in other years. Someone else might have it happen all in a few weeks, at some time between May and April.
In some regions, the variability of spring might be mostly early in Spring. Somewhere else the main hazard might be late, unseasonable, hard freezes. The criteria for a safe seed-start-time might be very different.
And Nature can only play the odds - I don't think the plants can predict weather. And if they did, global climate change would REALLY confuse them!
Maybe Maple catkins or avalanches work for one or another area, but some signs must differ regionally ...
... in my speculation.
