The best times to upgrade the watering can are the day before it is predicted to rain, as the rain will water the crops, or the 27th day of the [[Seasons|season]] after watering any crops that are expected to ripen on the 28th.
The [[Blacksmith]] will need 3 2 days to upgrade any tools, including the watering can.
[[Crafting#Sprinklers|Sprinklers]], which must be crafted and placed, will automatically water surrounding tiles every morning. Throughout the gameplay, sprinklers become available in 3 tiers that can water an increasing number of surrounding tiles, starting with 4 tiles (immediately adjacent to the sprinkler), 8 tiles (in the surrounding 3x3 area), and up to 24 tiles (in the surrounding 5x5 area).