Why do we fly so early?

The cool temperatures of the early morning hours cause the air in the valley to flow like a river, with subtle direction changes in the current at different altitudes. These conditions allow the pilot to navigate the balloon by changing altitude. Once the sun comes up however, conditions change. Starting in the late morning and continuing throughout the day to late afternoon, the ground surface is heated by the sun, the hot ground heats the adjacent air, causing it to rise like bubbles in boiling water. This boiling action destroys the stable flow of the air, thus destroying the ability to navigate.