Snowfall

Cumulative upkeep blue mana (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.) Whenever an Island is tapped for mana, its controller may add an additional blue mana . If that Island is snow, its controller may add an additional blue mana blue mana instead. Spend this mana only to pay cumulative upkeep costs.