Yes you can visit Delhi in August but this is not to be the best time to visit Delhi because its kind of hot. October and November or February and March are considered as the best time to visit Delhi. During this period, the weather remains pleasant. The temperature of Delhi ranges from 20 to 25 degree in October. In November, the temperature falls from 15 to 20 degree. Delhi experience the same temperature to some extent in February and March also.
Not really but due Independence day celebrations there will be tight security... so you hardly get to see anything ... visit when there is no national festivals
Delhi is hottest during April to July. In August temperature starts dropping however best time to visit is from September to November. during december to february delhi is quite cold and the temperature may drop to 5 ℃ in January