Below is a special kind of pollution rose I like to call an "Ozone Clock." This plot was from created with data at the Spanish Fork air quality site at the Airport. Imagine looking at a 24 hour clock with midnight at the top of the clock and noon at the bottom of the clock. AM hours are on the right half of the clock and PM hours are on the left half.
This plot shows the frequency of ozone concentration in Spanish Fork during the month of June, 2015. Ozone is most frequently at at healthy levels in the early morning hours between 6:00 and 9:00 AM. This is the best time of day to do some outdoor exercise. The worst ozone pollution most frequently in the afternoon hours between 15:00 and 20:00 (3:00 - 8:00 PM)