Here in Zone 5b snowdrops start blooming in October and continue with a few in each month through April. The majority of bulbs, however will bloom at the end of February into March. Here's a few that are still blooming despite snow and ice storms.
This is a Fall blooming elwesii originally from Montrose Gardens in Hillsborough, NC.
Galanthus elwesii 'Comet' taken on December 11th
This small planting of G. Potter's Prelude started blooming in November and it still going strong.
Steve