I think there's something in the idea that atmospheric precipitation affects plants differently from irrigation with water from other sources, but almost all my bulbs are grown under cover and watering them with well water from a hose doesn't seem to affect their growth and flowering adversely. However, those in the open often flower a little ahead of those in the frame. It seems that some kinds of bulbs respond more to moisture, and some kinds more to temperature. Many fall-blooming bulbs will flower right in the paper bags in which they're stored if they're not planted soon enough; presumably this is innate timing of some kind, since they will do this without any temperature drop. I have seen this in Colchicum, Crocus, Leucojum, and Sternbergia. One trick that's sometimes recommended to get recalcitrant seeds to germinate is to pile snow on the pots. Somebody told me more oxygen gets into the soil as the snow melts, but I don't know if that could be true. I've tried it and haven't noticed any clear effect. My seed pots are normally watered with well water, but some rain does blow in on them, since I keep them on the edge of a roofed deck. Jane McGary Northwestern Oregon, USA