After the sugar is completely dissolved, remove the pan from the heat and allow the mixture to completely cool. Hot nectar can warp or crack hummingbird feeders. To cool the nectar faster, place it in the refrigerator for 15 minutes, adjusting cooling time for the amount of homemade hummingbird nectar you have made. Do not add ice to cool the nectar; doing so would change the water-to-sugar ratio and make the nectar less attractive to hummingbirds.
Note: While the nectar cools is an excellent time to clean hummingbird feeders.