Place your flowers in a large bowl and pour over boiling water. Allow to sit at room temperature or overnight for the best flavor.
Strain the tea through a coffee filter or fine mesh strainer and try to squeeze out as much liquid from the flowers as possible. Set aside the dandelion liquid while you gather your canning supplies.
Fill your canner about 2/3 full of water and start heating the water while you make your dandelion jelly. Pour the liquid along with lemon juice and powdered pectin into a large saucepan and bring to a boil. With a wooden spoon, stir in about 4 1/2 cups of sugar and bring to a boil again, about 1-2 minutes. Turn off the heat and fill your half-pint or pint jars leaving about 1/4 inch headspace.
Process the jelly jars in a water bath canner for about 10-15 minutes. Remove the jars from the canner and dry off with a towel. Allow them to sit for 24 hours so the seals harden. If there are any jars that haven't sealed, be sure to place them in the refrigerator.