Pour the water into a large saucepan and add dandelion blossoms. Bring mixture to a boil and continue boiling for about 5 minutes, or until water turns yellow.
Pour the resulting tea through a fine-mesh strainer into a bowl, pressing the flowers to get as much of the color and flavor through the strainer as you can. Discard blossoms.
Place 3 cups of the tea in a medium saucepan and add lemon juice and pectin. Bring to a boil. Stir in the sugar and boil for 10 minutes, or until sugar dissolves.
Pour mixture into sterilized half-pint jars and seal. Store refrigerated for up to 2 months.