During the summer months when it is hot and sunny, ground-level ozone peaks.
Summer is usually the worst time of the year for air pollution.
The amount of ground-level ozone is not only determined by the amount of ozone forming compounds that are emitted into the air, but also by the weather. The reaction occurs more readily in the presence of energy from both the sun and warm temperatures. One by itself is usually not enough to form excessive ozone. Ozone is not a problem in Indianapolis during the winter because little ozone can be formed on cold, cloudy winter days. Another weather condition which adds to the ozone problem is stagnate air.