In high heat your bonds may soften. This is supposed to happen. The heat does not harm your bonds or compromise the integrity of your bond. The bonds will never "melt" out due to high heat or direct sun. It may be different from what you are used to with more "cemented" methods such as fusion or hot glues, but once you realize your extensions are very secure, and in light of the fact you are not harming, and losing, your own hair with extension wear, you will be pleased!
Don't pull at your extensions in 150+ degrees (like in a sauna for example.) Wait until you have returned to a cooler temperature until you brush, or tug, at your extensions.
Be careful not to hold your hair-dryer too close or place a flat iron on your bonds, you will remove them!
After drying with a hair-dryer, give your attachments a moment to cool before brushing.