I’m here in Chicago with four tickets to today’s race, which looks like it will be rained out. Presumably it will be postponed until tomorrow (Monday). When races are rescheduled for weekdays are start times usually the same time of day or are they earlier in the day.
And the answer is (of course), “it depends”. They will usually schedule the race as early as they reasonably can (they will of course aim for a predicted spot of clear weather), but IIRC rarely earlier than 12p. This is primarily due to travel issues for the team, those haulers got to get haulin’!