What time of day are the ground-level ozone levels the highest?
[Back to Top] Sunlight is necessary to start the chemical reactions that form ozone, and heat is important to make the chemical reactions more efficient. Ozone is primarily a problem during the summer months when long days deliver plenty of sunlight and when temperatures are warmest. In most areas of North Carolina, ozone levels peak during mid-afternoon through evening, when temperatures are higher, then drop at night, and are lowest around dawn. However, at high elevations (above 4,000 feet) in the mountains, ozone levels can remain high throughout the day and actually reach their highest values overnight.
