Heat 4 cups of the water and the sugar in a medium saucepan over medium heat, stirring until the sugar has completely dissolved. Do not simmer or boil. Remove from the heat.
Add the tea bags to the hot sugar water. Let steep until the mixture cools to room temperature.
Wring the tea bags into the tea, then discard them.
Pour the tea mixture into a large pitcher. Stir in the remaining water and the fresh squeezed lemon juice until well combined.
Serve over ice.
Notes
If your tap water has a noticeable chlorine taste or other treatment flavors, use spring water for the cleanest flavor.
Fresh squeezed lemon juice is recommended for the brightest, freshest tasting Arnold Palmer.
Honey can be substituted for the granulated sugar if you prefer a different style of sweetness.
Refrigerate leftovers in a covered pitcher for up to 5 days. Stir before serving if the drink has been sitting.