At North American tracks, races which are run on a turf (grass) course must sometimes be moved to the main dirt course, usually due to heavy rain or other adverse weather conditions; sometimes this switch is made after pick 6 wagering is closed.
At North American racing venues, events that take place on grass surfaces are sometimes rescheduled for the main dirt surface, typically due to inclement weather such as heavy rain; in some cases, this change is made after the closure of pick 6 betting.