I sweat buckets here in the Summer. From Mid June - Mid Sept the dew point rarely gets below ~65F (18C), and is frequently above 75F (24C). I weigh in at ~110kg and have a 13 mile ride so will purposely ride a bit slower to avoid getting too hot. Another strategy I use is to make sure I have at least one bottle filled with water only, for use in dousing my body as needed- this is especially helpful at stoplights where the hot pavement, idling cars, and lack of breeze make it exceptionally hot. On hot days when I do longer, 60 + mile rides, I frequently carry 2 bottles of gatorade and a bottle of water.
I have noticed that wearing a backpack in the high heat/humidity helps to keep me a bit cooler as it keeps the sun off of my back. The contents of the backpack can get very warm!