Dew forms when the air temperature drops below the dew point, which generally doesn't happen until about 6:00AM (except for exceedingly humid days and/or rainy days) at the peak of summer (when humidity is highest).That is also when the dew falls, I like DD don’t mow wet grass…
For reference, these are averages:
Indianapolis August 14 Weather, Average Temperature (Indiana, United States) - Weather Spark
On August 14, the temperature in Indianapolis typically ranges from 66°F to 82°F and is rarely below 58°F or above 90°F.
weatherspark.com
The average dew point at the same time of the year is around 64F. Average air temperature at 9:00PM is 75F.